Casio-F-91W die-shot | Hacker News Reader

Casio-F-91W die-shot

zeptobars.com

343 pointspicture155 comments

Have a look at this. Joey built a whole swathe of sensors to plug in to a f-91W like circuit. https://hackaday.com/2022/02/24/remoticon-2021-joey-castillo...

Also non-sensor applications: https://blog.singleton.io/posts/2022-10-17-otp-on-wrist/

I bought one of those recently and I was surprised by how inaccurate it was. It drifted like 15 seconds every month. From what I've been reading, that is normal, but I was surprised - with all the technological advances that we have it is odd to think that cheap timekeeping is not a solved problem yet!

Also: how is the software of these watches without a CPU designed? Is it something like Verilog or whatever?

>yet

I mean, we have accurate electric timepieces now, and the F91-W came out in 1989; we had accurate electric timepieces then, too.

it's a cost versus value thing.

It's easy to make a digital circuit that counts clock cycles with perfect accuracy. But for any clock, the actual length of each cycle is dependent on analog processes, and it's impossible to completely eliminate errors.

15 seconds per month is about 6 parts per million, which is already better than the manufacturing tolerances of a typical cheap quartz crystal. There are very few objects of any kind that you can obtain cheaply with that kind of accuracy. That suggests that, as this article says, Casio is trimming the frequency for each watch to compensate for component variations.

15 seconds per month is about 6.7ppm. That's well within typical crystal oscillator accuracy. If you need more than that (without external time correction such as gps or radio/internet), you need expensive oscillators with temperature compensation or even ovenized units.

> all the technological advances that we have

This is 34 years old technology. You can get GPS watches relatively cheap and they'd sync with satellites automatically and always remain accurate.

Yes. I ended up buying a GWM5610 which synchronises through radio. It's cool. But still I would have hoped there would be a better "local" (i.e. self-reliant) solution.

There's software for the Beaglebone PRU so you can generate your own WWV signal, for receivers buried too deep into buildings or otherwise suffering from poor signal.

Of course, with any HackRF you can also generate GPS signals.

But it would be a lot less necessary if the watches had reasonable temperature compensation. Obviously the crystal frequency shifts with temperature, and they're typically adjusted to achieve best accuracy when at "wrist temperature" for 16 hours a day, and "nightstand temperature" for 8. Any deviation from that, routine, and crystal accuracy gets terrible.

Temperature-compensated crystal oscillators (TCXOs) switch tiny capacitors in and out of (or bias a varicap in) the crystal loading circuit to "rockbend" its response and keep it nearly flat across a wider range of temperature, but this requires extra power. A minuscule amount, but it adds up quickly when your budget is nanowatts.

However, there's another way to do it, which I'm astonished not to see: You don't need to alter the crystal's actual frequency if you can just adjust the number of counts that represent a second. Every once in a while (every few minutes would be plenty), take a temperature reading, look it up in your calibration table, and stuff or steal a few cycles from the counter register.

This takes basically no additional power, adds one more calibration step at the factory, and should bring drift down by an order of magnitude, into TCXO territory. Seconds per year, not seconds per month. That would be something to crow about, and it baffles me that Casio and others never went that route.

Nxp sells a PCF2131 with an internal TCXO that runs on 64 nanoamps when not doing anything else. So with a modern CMOS process, the TCXO itself is not a big deal. A clock pin at 32768 cyc/s looks to be way more power hungry, which tells us that an ideal low-power solution is an all-in-one SoC.

Last year I switched to the GWM5610 after a long search. It perfectly fit my needs - accurate all the time (syncs to atomic clock radio signals), never needs a charge (solar powered) and is indestructible. What more could a nerd want!

At around 1976-1977 I bought one of those fancy new LED wristwatches, where you pressed a button and the time lit up in red. Straight out of James Bond, as I recall.

As I was studying electronics at the time I brought the watch to the lab and opened it and connected a frequency counter to the oscillator, you could clearly see the crystal and a little trimming pot (I don't remember by now if that was a pot or something else - capacitor maybe), and adjusted it to exactly 32768Hz.

After that the watch drifted less than one second per month, and it kept the stability for the rest of the year (until a bicycle accident which resulted in a smashed watch).

I've never since owned a watch which was even close to that. They're drifting so much that I can't even rely on my watch to catch the bus (there's a stop outside my home and the bus is there exactly on time).

People who are curious about this, it's worth reading about quartz oscillators in watches and in particular, methods of calibrating them: https://en.wikipedia.org/wiki/Quartz_clock#Inhibition_compen...

Get a Casio G-Shock. The 800 models can sync with your phone and the time is auto corrected. I bought a GBA-800 from a pawn broker - out of the dozen or so watches in my box it's the one I reach for if I have to know what time it is accurately.

One of my best bang-for-the-buck purchases was a Casio Waveceptor watch with a hybrid clock face.

The watch uses the WWVB signal for nightly syncing. However, living on the East Coast means syncing is very dependent on day-to-day atmospheric propagation. When I visit more inland, it works great.

The watch face is solar powered, so I’ve never had to change the battery.

It has since been retired after 8 years of use for an Apple Watch, but I think fondly of the mighty job it did.

I love my cheap waveceptor which is always, always accurate.

Actually in the process of choosing a casio lineage (waveceptor movement, metal case, sapphire crystal) - do I get titanium or blacked out stainless steel, lol

Absolutely, get a G-Shock. But get one which radiosyncs. Most phones (and PCs), although synced by internet, reliably lag between one and two seconds.

My synced G-Shock is always correct to within better than one tenth of a second, that is, to the limit of observability. Solar powered, too, so it's just an utterly reliable black box. My favourite gadget by far.

Radio syncing isn't available in my country (no local transmitter and too remote to pick up other countries) so phone sync is preferable for me.

> Most phones (and PCs), although synced by internet, reliably lag between one and two seconds.

NTP isn't nearly that inaccurate.

No, of course it isn't. I said most phones (and PCs). Clients often seem to lag that second or two, reason unknown, but I've always assumed due to software bloat, unstrictfulness, and indirection.

I just checked the price for one of the digital G-Shocks.. I could buy a car for that! A used car, at least. So no, I'll stick with the cheap digital Casio I already have, even if it's a couple of minutes wrong today (it's a bother to adjust them all the time). At least I don't have to worry about one thing: Battery. It seems to run forever. I think the battery was supposed to last 7 years, but by now it's been twice that long. The backlight still works as normal too, if I press that button.

My f-91w gained less than a second over several years... While it was sitting on my desk in a giant climate controlled building within a degree of 22C year-round. When I wore it, it deviated quite a bit more, but still far better than the 30s per month quoted. I was very excited with my experiment at first comparing it to a friend's HAQ that he did wear. Then I realized the flaw in my method.

> and the bus is there exactly on time

So that would locate you pretty unambiguously in Switzerland then?

Heh no :-) - because the railway stations here don't have station clocks with second hands, unlike Switzerland.. heck I don't know why they bother with the minute hand.

> At around 1976-1977 I bought one of those fancy new LED wristwatches, where you pressed a button and the time lit up in red.

This was the vibe I got when the first pre-always-on Apple Watches were first introduced with Raise to Wake - where you had to actively do an action to see the time.

> the bus is there exactly on time

What's winter like in Japan? Is it freezing?

Almost all quartz watches have a similiar movement, running of a 32kHz crystal. Those give you about 15s/month accuracy, which is an oder of magnitude better than most mechanical watches and that for a very few bucks. More precise quartz watches exists, but they require quite a bit more effort, which of course translates into costs.

Actually one of the earliest quartz watches on the market from Omega used a 2MHz crystal and was very accurate. Personally I own a Seiko with a 200kHz system, which is good for about 20s/year. Then there are the thermo stabilized systems, which are even more accuarate. The problem is, that the frequency of the crystal depends on its temperature which is the main source of time inaccuracy (there are some watch enthusiasts which do get egg breeding cupboards which have constant temperatures up to tenths of degrees, they make for very accurate watches).

Currently, the best movements on the market are accurate to about 5s/year, which is pretty amazing considering the watches are worn on your wrist in varying conditions. With my precise Seiko watch I could even notice a slight change in speed when I moved quite a distance to a different town with slightly different weather. That shows how big a challenge a really accuarate wrist watch is.

Then there are the market concerns. The most basic and cheap quartz are already accurate enough for most non-enthusiasts. Then, after almost being killed by quartz watches in the 80ies, the luxury watch industry managed to establish a mechanical movement as the desirable item. So there are few expensive quartz watches left on the market, which would feature more sophisticated movements with higher accuracy. And finally, there is a range of higher value watches which receives time signals, be it official time signals in several regions or just GPS signals.

Cornered like this in the market, unfortunately not much money went into high-precisions movements. There are still a few on the market from Seiko, Breitling, Omega and Citizen (there might be more, but those come to my mind). And of course there is the Apple Watch, which is rather affordable and just uses NTP to get absolute precise timing.

To add to this—I’d say that watches are quasi-temperature-controlled. You wear the watch in varying conditions, but most people spend most of their time in controlled environments, and the watch is directly next to your body, which itself is temperature-regulated. This just means that temperature drift may be less of a factor for watches than it might be for, say, a clock on the wall or in a car.

Assuming you wear the watch.

Indeed, another challenge is crystal aging. For example, PCF2129 has an aging offset register. These devices are rated to +-3ppm over the huge range of -30-80C but the register allows for -7 to 8ppm offsets, if necessary.

Citizen has a movement where they throw all the tech they have at it to guarantee 1 second per year accuracy. I remember things like quartz crystals have aging effects, so they used pre-aged crystals - little details like that. It even has an anti backlash mechanism on the second hand so that it ticks perfectly with no visible wobble. It probably doesn't make sense when it would be much cheaper to just use an external radio/GPS time source, but as a watch company, it makes a statement about their craft.

There are other high-accuracy watches (it's mostly a Japanese market thing), and I believe +/- 10 seconds a year is considered fairly pedestrian in that world.

Citizen has a quartz movement that is rated to only drift plus or minus 5 seconds a YEAR which is quite impressive though they cost around 2000 dollars and are exclusive to the Japanese market. Several other brands out there make high accuracy quartz movements (which is done with thermal compensation) but they do generally cost more than cheap Casios.

While 15 seconds per month is within Casio’s spec for this, it’s also worth noting that there’s reportedly a lot of counterfeits of the F-91W floating around. I got one once from a major marketplace.

~1s per day is normal for a non-temperature-compensated quartz crystal. The cheap solution is to just sync to LF time transmissions (or GPS if not running on battery power).

The F-91W might not actually have anything resembling software; just fixed function mixed-signal circuitry, but I haven't investigated it. Given the timing of its release, it's possible that an HDL was used, but also possible it was designed at the circuit level with CAD. The F-87W (which the 91W replaced) predates either VHDL or Verilog.

A fair assessment, but I find it funny that 15 seconds per month is considered inaccurate, analog watches would kill for that sort of accuracy, a railroad quality pocket watch for example must loose no more than 30 seconds per week. I would guess that as smartphones are replacement for the pocketwatch, The way their network connected, never drift clock works becomes the new normal.

I have to admit, for my day to day use I am happy if I am less than five minutes off.

You mean Mechanical watches, not Analog ones. There are lots of Analog quartz watches with 15s/month accuracy.

> analog watches would kill for that sort of accuracy

Seiko 5 automatics have been reported to lose 30 seconds a month, even as little as 12 seconds a month.

my automatic Aqua Terra (8800 movement) maintains this (or better) accuracy, which i find astounding for a mechanical gear train that oscillates at 3.5Hz. i definitely would expect a well-tuned quartz movement to outperform this significantly. but i guess not for < $20 :p

You might be surprised to learn a lot of servers even have largish time drift. I might be repeating info which is getting out of date but I heard 30 second drift isn't uncommon. Obviously doing NTP syncing more frequently would probably help that.

Yeah, the React Native debugger is broken on my Pixel because the time is different from my laptop by ~0.5 s, so short taps register as long presses or something like that.

If it's comparing times from two different devices, then it's not broken because of the difference in times.

If it's broken because the designer assumed any two devices would have a sub-second time difference, it's still broken.

Yes my point was to say that it's broken.

Oh I see, I misunderstood initially but I got it when rereading.

The functionality of the F-91W is simple enough that I don't think a CPU would even be needed. Probably the digital parts of this chip are just state machines. That being said, the left half of the die shot looks like some kind of gigantic ROM, which could either be used by a CPU (as static program memory) or just transition logic/data for any generic state machine(s).

Verilog came out in 1984, but its use for synthesis (i.e. actually compiling text into circuits) was not popularized until much later, after correctness bugs in synthesizers and various other advancements in design tooling came around. It might have been used as a simulation/verification language for the digital portions of this chip.

vhdl started as a project to document integrated circuits. The department of defense was getting a lot, and more complicated, integrated circuits and wanted a standard to document the functionality. At some point someone thought, "you know, if the documentation is good enough we could reverse it and synthesize a circuit from it", and thus why you use vhdl(or more likely verilog) to program your fpga.

The two languages fill the same role in the ecosystem, I have to say that I have never used ether, but my impression is that vhdl has clearer syntax(if you can stomach it's ada look and feel) and verilog has better tooling. which makes sense considering that one was a documentation project and the other was an internal tool for simulation that escaped into the wild.

Anecdotal but my F-91W is currently 8s behind my phone, which I sync'd together about 6 months ago. I've always felt very impressed with how accurate it is.

I was surprised by this inaccuracy too. But was impressed when I learnt that there is no analog wristwatch that can match this accuracy - they are all far far worse. (Isn't it shocking that all those super-expensive Rolexes and whatnot are all going off by minutes per month!) Get one of the Casio watches that syncs to atomic clock radio signals every night - it will be second-accurate all the time.

> But was impressed when I learnt that there is no analog wristwatch that can match this accuracy

Seiko 5 automatics apparently[1] can.[2]

[1] https://www.watchuseek.com/threads/seiko-5-is-pretty-accurat...

[2] https://qr.ae/prvf6L

According to the linked thread, the Seiko 5 is an order of magnitude worse… 5 seconds per day, versus 15 seconds per month for a quartz watch.

This one?

     After observing Seiko 5 SNK809 for 35 days, I can say I´m happy with accuracy.

     Overall, it has lost 25 seconds during this time.
     It lost most of it when it was sitting on table 2 times during observation. When kept on wrist, it hardly lost any...

It will be calibrated for room temperature, temperature changes do affect the oscillator frequency that is why highly accurate frequency sources have an "Oven" to keep the temperature stable https://en.wikipedia.org/wiki/Crystal_oven

F-91W is the watch I wear today.

Actually, my favorite wristwatch - or rather the one I wore for 25 years or so - was a W-71. Unfortunately, you can't buy these except as vintage second-hand. I still don't understand why that is... I always felt it a more "aesthetically-balanced" version of the F-91W; plus it had 4 buttons rather than 3, which makes sense given the structure both watches. But I lost my W-71 while moving out of my last apartment, so... now I've had to settle on the F-91W. Ah well.

I don't wear watches as I'm always either at my computer or have my phone with me, but if I did wear a watch, I would probably go with something like the F-91W. Images of it bring on a nice retro nostalgia, and I appreciate its blatant function over flair aesthetic.

Umm, perhaps you haven't seen the W-71:

https://duckduckgo.com/?q=casio+W-71&t=ffab&iax=images&ia=im...

not exactly flair aesthetic.

This is a remarkably interesting image. How do these guys even get these shots? I'd love to do this on all kinds of things at home..

I really like this one Defcon talk on chip decapping [1]. It's a pretty nasty process but absolutely one you can do on your driveway (poor man's fume hood, don't tell the EPA) at home. You can then just use a standard front lit microscope to take die shots.

[1] https://youtu.be/0Z4aF-qiziM

For die photos, you want a metallurgical microscope, one that shines light down through the lens. A typical microscope shines the light from underneath, which works well for biological samples, but not so well for chips.

The tricky part is decapping the chip. The easy way is to get a ceramic package, which you can decap with a chisel. Or a metal can, which you can open with a hacksaw. With a standard epoxy package, you can heat it with a hot air gun and twist it, and you have maybe 50% chance of the die separating from a package. The best way for epoxy packages is boiling sulfuric and/or nitric acid, which has obvious issues.

The other aspect is that you need to stitch together a bunch of images to get a high-resolution photo. I use Hugin, which lets just say that it has a learning curve.

Have you tried ImageJ, specifically the Grid/Collection Stitching? I use it for microscope stitching and it works pretty well.

I tried it at the beginning, but found it quite complicated. A the moment Hugin is used, which works nearly perfectly, especially on XY stage where you can disable frame rotation optimization.

This same site has an article on laser decapsulation not too long ago:

https://zeptobars.com/en/read/laser-decapsulation-fail-not-s...

It appears to not work so well, but the video looked very cool.

Thank you for your informative answer.

Some time ago I posted exactly about that : https://zeptobars.com/en/read/how-to-open-microchip-asic-wha...

My latest microscope is this one, but Casio photo was made by temporary microscope I assembled from Thorlabs & Olympus parts: https://3.14.by/en/read/olympus-bx60-fluorescence-metallurgi...

I found this book to be quite beautiful. It even says how they did some of the shots at the end. https://nostarch.com/open-circuits

Seems like two large similar rectangular logic areas.... maybe one is state machine and one is display?

Or maybe one is clock/date and one is UI?

I think it's one blob of standard-cell logic on the left with power routing through the middle. I don't think there is any visible partitioning into functionality in this logic. The large amount of analog circuitry in the right half is a bit of a puzzle. It looks like some large capacitors, maybe a charge pump for something?

This is outside my wheelhouse, but I assumed that the large capacitor area was a (trimmable) capacitor bank that could be put in parallel with the load capacitor on the (external) quartz oscillator, allowing calibration to counter some unit-to-unit variant in crystal frequency.

That's a possibility, but I don't see any laser-trimming marks on the big capacitor. Another option would be selecting capacitors with fuses, but I don't see any fuses or capacitors with powers-of-two sizing. With the complexity of the circuitry in the right hand side, I think there are a bunch of analog things going on.

The calibration for quartz crystal variance in these watches is done much, much later in the manufacturing process using solder bridges on the PCB - people have reverse engineered it. I think there are watch oscillator chips out there with one-time programmable calibration (particularly for analog watches) though.

Is that a Swiss flag on the lower-left corner, or some kind of pads?

Maybe a fiducial marker?

Correct, this is an alignment fiducial for doping to ensure everything is in proper rotational alignment before masking and doping.

Maybe an alignment marker for layer stacking.

Yup! These sorts of crosses are used to align photolithography masks. Here's a similar example: https://www.seas.upenn.edu/~nanosop/images/alignmentmarks2.p...

There are a lot of other structures used to characterize the alignment and other fancy structures which support machine alignment for newer (than like the 90s) processes.

Possibly a (coarse, as it's the topmost) mask alignment target.

> Casio F-91W is an iconic watch worn (among others) by Barack Obama and Osama bin Laden.

This escalated quickly.

it's infamous for being used by terrorists to build IED thanks to its accuracy and durability (same goes for Toyota Hilux), I think it's notoriety went that far that if you worn it at airport you might have been selected for random security check, though not sure if this part is truth or myth

Looks like a city from overhead. Amazing.

"The Grid. A digital frontier. I tried to picture clusters of information as they traveled through the computer. Ships, motorcycles. With the circuits like freeways. I kept dreaming of a world I thought I'd never see. And then, one day... i got in."

I guess you'll enjoy this one too: https://zeptobars.com/en/read/AD9361-SDR-Analog-Devices-DAC-...

There's a reason why "circuit as a city" used to be a common visual metaphor in pop culture when computers came up. E.g. this scene from the Hackers:

https://youtu.be/IESEcsjDcmM?t=135

Funny timing: I saw Koyaanisqatsi for the first time tonight, and there’s a section where it cuts from satellite images of a city to microchips (https://youtu.be/RSINqSvSVyM?t=402)

It made me want to look up more pics of chips, but after not getting good results searching on my own I gave up and came to HN... only to immediately see this post :)

Dumb question: is it legal to share a die shot like this one? What does copyright law say about this?

I mean, yes, the author took the photo himself but what about the underlying material? Can I share a photo of an entire book? Do I own the copyright to a photo of a painting?

why not? you are free to disassemble your computer and take photo of motherboard or whatever hardware you have, I don't see how is taking photo of die different

you can have copyright to your own photo, but not to pictured design

Well a die design, just like code, is definitely some form of intellectual property and covered by copyright law. So I think a more fair comparison would be a photo of an entire book.

It might be a problem if the photo was reverse engineered into a schematic, which would also imply much more detail, but in this case it's just a photo of something cool.

> Well a die design, just like code, is definitely some form of intellectual property and covered by copyright law.

you can consume a book just by looking at it. You can't "read" a die-shot as easily.

The die design tells what parts are there, not their values or characteristics; cloning a chip just by looking at the die would require a lot more research.

> is definitely some form of intellectual property and covered by copyright law

I'm not sure if you meant to suggest that "some form of intellectual property" implies "covered by copyright law", but this is untrue in general, and untrue in this specific case.

Copyright does not cover mask works; see [1] for discussion, from which quote: "Copyright law ONLY protects an original work of authorship IF the work is non-functional. But the etching designs on computer chips ARE functional."

[1] https://revisionlegal.com/copyright/mask-works-101-copyright...

Chip dies are covered by a special mask copyright law - you can actually see the M with a circle round it in this die photo (rather than the more traditional C with a circle)

"Can I share a photo of an entire book?"

No is the short answer to that one.

Actually you can share a photo of an entire book - it's only that you can't share photos of all its individual pages as well...

(Sorry, tried hard to resist, and failed.)

In the US, semiconductor mask layouts are not eligible for copyright. Instead, the mask layout is protected under the Semiconductor Chip Protection Act of 1984. The Act grants rights similar to traditional copyright, but with a shorter period of protection and a more permissive framework for derivative works.

Notably, the "shorter period" is only 10 years.

Interesting, I imagine under normal copyright this would fall under fair use, does that exist for this as well?

If the layout had copyright protection, this would still be fair use.

I don't think it is any different than taking a photo of your car engine or gearbox or any such component.

Issues comes when you start to make copies.

Yep, this is my understanding.

Also, world practice shows that noone ever got into troubles for posting chip pictures, and in 10 years noone ever contacted me to remove any photos.

But companies do get intro troubles for trying to do copycat chip production, although it is not always easy to prosecute.

From the business/design/technology POV, why is this watch so successful and so iconic?

It's durable, keeps good time, battery lasts 7-10 years, clear display, thin and light. It's incredible value for $15-25. Deserves to be as popular as it is.

The only real drawback is the terrible backlight which is fixed by the F-105W which has a soft blue EL backlight <3. Much preferable to the 91 IMO. Functionally both watches are the same.

I have probably ten- not precisely the same model- in the past thirty years. Most common failure is strap breaks after taking the watch off for swimming every other day. Second most failure is to shatter a corner due sports- hit my wrist on something. Third is a humidity leak when I visit the US South in the summer.

A piece of art.

best watch ever!

I'm a big fan of the F105W which is basically the same watch with a vastly improved backlight that lights up the whole LCD. It makes a great watch extremely usable at night.

I'd also recommend the Casio G-Shock GWM5610 which admittedly is about 5 times more expensive at $111 but it has UTC time and is absolutely bulletproof, along with radio sync and solar with solar charge indicator. It's currently my favorite among my modest under $200 collection of watches because it's so practical.

I love unconnected watches because they tell the time and have a few other basic features without vendors competing for your eyeballs in constantly evolving ways.

Side note: I'd avoid Seiko even though they kicked off the quartz crisis by launching the world's first quartz watch in 1969, their product quality is crappy these days with missing features on some nice looking watches, and some bugs in their mechanical movements.

On a separate note, I find the luxury watch market to be quite hilarious (especially the pretentiously eloquent way a customer will describe their "acquisition") but I do keep an eye on it for fun and classics like the Rolex Sub Date have dropped by over 20% in price on the used market in the past 10 months (source is Chrono24 which charts prices). My guess is we'll see the used luxury market flooded in 2023/24 as extravagant purchases made during boom times are liquidated for cash.

>radio sync

Such and underrated feature! There is a good list of Multiband watches that works across multiple continents that way

https://shockbase.org/function_page_dyn.php?function=multi_b...

> F105W which is basically the same watch with a vastly improved backlight

Can’t stress this enough. The F-91W is useless at night because the backlight brightness is terrible. The F105W has an indiglo-style “EL” light that is very effective. The two watches are nearly identical from an aesthetic perspective. The functions are identical as are the buttons.

Indiglo has good looks and function. What I dislike is that it requires a high-voltage driver. As tiny and low-current as that may be, it is electrically and even slightly acoustically noisy, and not something that belongs in a low-voltage wristwatch.

Considering I might turn it on once per night for a second or less, I’m not concerned. Is the risk that it affects the timekeeping?

Why not? An incandescent backlight _physically gets hot_, I'd argue that has even less place in this application. It's just what they had at the time.

But in either case, it's perfectly safe. There's no way to touch either the hot parts or the high-voltage parts. And even if there was, the battery doesn't have enough oomph to do anything more than tingle once the prickly part was trying to drive something as massive as a fingertip.

I noticed the noise too, when I owned one, but I figure silencing it would've cost size, weight, and power. And the noise was never more than a curiosity, so I'll take it!

They aren't talking a out safety, they're talking about efficiency and accuracy. A boost converter is inefficient and you don't have power to waste like that in a watch. And electrical noise perturbs the timekeeping parts.

However your comparison to incandescent and your point about the momentary nature are both valid I'd say. If they had magic, they'd have used it. So they took something fundamentally inefficient and added engineering to make the best of it. A bad thing, done as well as possible,

You could say almost the same things about incandescent. It's not electrically noisy, but temperature sure does perturb the timekeeping, and incandescent definitely wastes power. Especially if you need the filament to last indefinitely instead of replacing it easily.

I've never had any problems with my f-91w at night. I can't use it as a reading light like the EL backlights, but it also doesn't ruin my night vision.

How does the brighter backlight affect battery life? Doesn't the original model have a 7-year battery life?

I think EL uses less current than an incandescent, which is what the F-91W has. Anyway, the battery life always lasts longer than the band for me. Years. I replace it when the band tears, which is before the battery dies.

Is it incandescent!? I would have expected an led, or at least a process improvement where it was replaced by an led.

It’s still an incandescent, unfortunately. If they changed it to an LED, it might be bright enough to be useful.

Allegedly, it's LED now:

'The small light bulb was replaced by a LED diode, but the intensity of the tired firefly remained'

https://www.hodinky-365.com/blog/casio-f-91w-review

I wear F-91W every day and FWIW, the light is adequate to see time at night.

I love my GWM5610, the only thing I dislike is how hard to press the buttons are and the bad display angles. But other than that it's a damn brick. And the radio sync is magic.

I had been wearing the F105W for about two decades and then decided that I want an upgrade. I tried to get as much value for my money and ended up buying the LCW-M100TSE-1AER from Casio's Lineage collection for 240€. Features are

- Titanium casing and strap

- sapphire crystal glass

- Wave ceptor (radio signal receiver)

- Solar cell

- Light (not great, but usable)

If Casio combined these features in a classic looking LCD watch that does not cost a fortune, I would not only buy one, but three of them. I know, there is the MRG-B5000D-1, but with a price tag of 3500€, which is more than then times the price of my watch with fewer features (no waveceptor) this is a bit expensive IMO.

I don't really understand your comment about avoiding Seiko (and yes as a Seiko collector I'm a bit triggered). In my experience Seiko makes absolutely great quality watches still with maybe the only issues generally being the occasional misaligned chapter ring though I pretty much only collect Seiko mechanical watches so maybe the situation is different with their quartz watches.

Citizen also makes some particularly interesting quartz watches the Chronomaster series (which is a Japanese domestic market exclusive) has one of the most reliable watch movements ever with a rating of +/-5 seconds a YEAR.

Seiko 5 automatic movement is on a par with the Rolex automatic movement according to my friend who is an official Rolex repairer.

They are often quite similar in design though I'm guessing the Rolex uses quite a bit higher quality materials.

Quality of Seiko 5 is pretty good, but IIRC the Rolex movement is more compact.

Well they're both Automatic mobements with a Swiss lever escapement design, but the Rolex is finished better and has better balance adjustment (free-sprung balance). It is also factory adjusted as opposed to the Seiko 5 movement.

I'm in the same boat, won't ever touch a seiko and refuse to do so for for 2 main reasons:

1. They have the gut of naming their watch "save the ocean" and doing things with PADI when the country they operate in is involved in commercial whaling, still go on fishing species of tuna that are on the verge of extinction or throw sharks back in water still alive after removing their fins just to make some soup. That's appalling, if North Korea would make a watch called "human right" we'd all laught and move on but, I'm not to support a company that make "dive watch" pretending to care about the ocean and not saying/doing anything toward what's actually happening in the country they operate in.

2. I'm a yema fan boy and seiko used to own yema in the 90s. Under their stewardship, they introduced plastic to hold the movement in place instead of the previous metal piece and did change the case onto a cheap low cost copy of what was available before and removed the original hands by some mercedes hands, copying everything Rolex was doing in a cheap package. That period in Yema's history was terrible, hopefully they ended up selling the brand after a few years but boy how did they make a mess

Well I don't know that Seiko has been directly involved in whaling in any way and some of the proceeds from the "save the ocean" line are given to divers that work to remove marine debris so that seems like a really odd connection to make.

I have a casio g-shock MTG with solar and radio sync that I bought more than 10 years ago. Wear it almost every day. Battery indicator is still at full. Once I had to buy a small metal rod (for a few euros) for the metal strap, and still going strong.

Casio is an under leveraged brand. One of the few that could, I think, be taken into more product areas than it is currently. There's brand equity there they are not fully leveraging.

Though not a move into a completely different product area, it's been interesting to see them step up their digital piano game. For a long time it seemed like Casio had a reputation for not making serious keyboards that you could gig on. But they have been churning out really nice keyboards recently - most notably, the Privia line. The ones I've played have a really nice feeling action, pro-level sounds and they're visually quite slick.

I was shopping around for a digital piano and the Privia does look really nice. I haven't experienced one in person yet and I am a bit scared to buy any keyboard or digital piano without trying the action.

I like the action on the Privias (and the similar CDP360s, which I played recently). My only complaint about the action is that if you're playing at low/practice volumes, you tend to hear a lot of mechanical plastic sound as the keys spring back up. I'm a big fan of Roland's actions. I'd check out the FP30. I also used to practice on a Yamaha P125B and they are great.

Thank you very much for the additional info!

I am always attracted to the design of Casio keyboards when I see one at a store somewhere. Then I play them, and realize that many of them (the low end models) still often lack velocity sensing. Both the best and the worst thing about Casio is that they’re stuck in the 90s.

But why?

Do we really want and need a Casio rice cooker?

And since they're specialists in cheap and reliable watches (and calculators and few more things), what would happen to their brand if the rice cookers were shitty?

This is a somewhat weird: do you judge Sony headphones by how good Sony cameras are, too? Or Samsung phones on how good their TVs are? Because how good a Casio calculator or rice cooker is, is entirely independent of how good their watches are?

This seems to be backwards: you judge a brand based on how all its products perform, and if the balance tips towards "most are shit" then it's a shit brand. A brand making lots of things and only one shit (type of) thing, then it's "they're great! Except for their X, don't buy those".

Well.. yeah. If you bough a samsung phone, and it was full of shitty adware and preinstalled apps, would you expect their tablets, smart tvs and fridges to be any different? And are they?

Yes? And yes? You're asking this like it's a bizarre thing to do, but that's how you think about consumer goods as adult: if you dismiss an entire brand conglomerate because of a single product line, that's an incredibly weird way to think about products.

If Samsung phones are bad, don't buy (another) Samsung phone. But when you need a dish washer, and reviews say that Samsung's is the best bang for your buck, their adware-laden phone has literally nothing to do with the decision to buy the Samsung dish washer. They are completely different products, made by completely different factories with completely different QA processes, and completely different target demographics.

Don't judge brands, judge product lines by brands. Because quite often, the people making one thing have nothing to do with people making another thing, they're completely separate "we can't call them companies on paper but in practice that's exactly what they are", and the owning brand itself has barely anything to do with the products they make, unless it's their major brand-recognition product.

I just want to note here that Samsung refrigerators and dishwashers are absolute shit and should be avoided like the plague. Also, their stoves are pretty crap, too, with a self-clean option that destroys the motherboard and blowers.

You'll have a hard time convincing me that their design and manufacturing issues are not endemic across their entire company. Fish rots from the head, etc.

Much like the other commenter: yep, Samsung's not a good company, making it all the more appropriate to use as example for "judge the company on all its products, not just one".

But if samsung put ads and bloatware on their phones... won't they put them on TVs too?

Oh wait, they do:

https://old.reddit.com/r/assholedesign/comments/co5aw4/unrem...

What about on smart fridges?

Oh wait.. they do that too:

https://old.reddit.com/r/legaladvice/comments/yr80x3/my_smar...

Good: you did your research and discovered that Samsung's a mostly shit company. We already knew this of course, that was the whole point of using Samsung as example for "do your homework first, then judge the company".

I personally would, yes

Samsung is the perfect example actually. Their TVs ship with a weird Android that breaks half of the Vanilla Android features. So do their Phones and Watches.

Recently I got a new dishwasher and wasn't surprised to read that the controls of Samsung dishwashers can be somewhat weird and quality is questionable as well.

Yes, that was the point of using Samsung as example: judge the brand on all their products. Samsung is a terrible company, because all their products are pretty terrible. Not because "their phones are".

FWIW, they're also specialists in expensive and reliable ruggedized watches (G-Shock, especially the higher-end variants with compass, GPS etc).

Casio has leveraged the love for the G-Shock with watches like the $4,000 MRGB5000BA-1 as others in that line. Keep in mind that the Casio brand sells everything from instruments to label printers and calculators, which presents a challenge when it comes to targeting e.g. it can't be a luxury watch brand like Rolex because it's too broad (Rolex just sells watches). You also can't narrow the brand focus to watches because you may harm other lucrative business divisions like musical instruments. Casio means many things to many different markets.

Apologies for a silly question, what exactly are we looking at here? I've seen the inside of an F-91W, and I always imagined that under the black epoxy blob was some kind of off-the-shelf microprocessor (most likely 4-bit) with a mask ROM containing the watch's logic. Is the entire watch run from this IC, with no processor? If so that's really interesting.

If you are making millions of units for a RT application you definitely want custom silicon.

Is this on account of cost, or simplifying verification? I was under the impression that minimising the overall risk of a design was a major consideration. I'd love to know more about how these design decisions were made.

Power consumption and cost. 10 years on a battery is very hard to achieve for microcontroller.

https://sorwatch.net shows that : with much more advanced microcontroller (much more modern tech.node, low power features) - it only works for 1-2 years on a single battery after extensive power optimizations.

In custom silicon when seconds tick - it's maybe 100 transistors change their state. In microcontroller - it's roughly 10'000-100'000 transistors changing state to handle interrupt and update display content...

Is the F91W still manufactured in Japan?

It is made in China afaik.

I've seen some made in Thailand. I would expect chip itself & quartz oscillator made in Japan.

Does it run Doom?

Not... yet :-)

Maybe eventually: https://www.geeky-gadgets.com/casio-smartwatch-22-07-2022/

Gonna need some creative solutions for graphics rendering, though.

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