PC-Retro Motherboard Kit: Build a faithful reproduction of the 1982 IBM PC 5150 | Hacker News Reader

PC-Retro Motherboard Kit: Build a faithful reproduction of the 1982 IBM PC 5150

mtmscientific.com

Related to IBM PC keyboards

Unicomp modern versions of the IBM Model M keyboard built iwth the same tooling that made the originals. When living in a flat share I had access to a IBM Model M keyboard the one made for the PS/2 computer. This is one of the best keyboards I have ever used they are built like tanks.

Unicomp keyboards https://www.pckeyboard.com/

I tried a "buckling spring" keyboard (I think from Unicomp) that was supposed to be the equivalent of one of those IBMs and I was severely disappointed in the electronics. It could not handle multiple keys properly the way a real one would. Basically they had focused completely on the selling point of the springs and neglected to make a usable product.

(I did have a real PS/2 Model M previously, so all I really wanted was a USB equivalent)

The USB HID standard has a limit of 4 keys pressed at once, unless you do fuckery like virtual USB hubs with additional virtual keyboards (which will cause some things to misbehave) there is no way around this restriction without custom drivers (which are also a nightmare).

This has been debunked several times over the years at Hacker News. The standard imposes no such limit; additional HIDs are not required in order to exceed that number of keys; and properly written ordinary HID drivers can handle what is necessary, as it is an ordinary part of the specification to describe the size of the input report and an ordinary part of a driver's operation to decode and process an input report descriptor in order to know how to decode an input report.

* https://news.ycombinator.com/item?id=8191260

* https://news.ycombinator.com/item?id=7358911

* https://news.ycombinator.com/item?id=8478042

No, the basic mode has a limit, and most keyboards keep using it due to (lack of) legacy bios support.

TIL

By chance, do you know the limits on real PS/2?

Effectively none --- the keyboard only sends "key X is pressed" and "key X is released" messages.

On the other hand, the key matrix design can impose its own limits.

To expound on that: The matrix in most PS/2 keyboards only supports two-key rollover (reliable detection of two keys pressed at once). In the case of three+ keys there is a chance for missed presses and other artifacts.

Thanks as well.

Cool, thanks.

Built like a tank is right, the thing weighs nearly 5lbs. You could beat a man to death with a model M and still use it afterwards.

I've used a Unicomp "Spacesaver" for many years and have been very happy with it. Recently I've switched to a ten-key-less keyboard with blue Cherry switches in order to have more space on the desk, and I've got to say that I much prefer the snappy feel of Cherry switches.

I've always been bothered that Unicomp uses the term "Spacesaver" for their keyboard with less trim; traditionally, a Model M Spacesaver refers to a ten-key-less.

The big difference in the feel between buckling spring and MX blues is that buckling spring has a tactile drop where the force suddenly drops off right at the actuation point[1][2], where blues have a tactile bump where the force spikes up right before the actuation point[3][4]. I'm not sure what it's called, but the blues also have a temporary drop-off in pressure in the middle of the return stroke.

Which is better is a matter of personal preference. There's no substitute for actually trying a switch, but actual force/displacement graphs will do a much better job of telling you what a switch feels like than subjective words like "snappy" or "smooth" or "mushy". https://input.club/the-problem-with-mechanical-switch-review...

[1]: Model M measured: https://input.club/the-comparative-guide-to-mechanical-switc...

[2]: Model M nominal: https://upload.wikimedia.org/wikipedia/commons/3/31/Fig_2_ha...

[3]: MX blue measured: https://input.club/the-comparative-guide-to-mechanical-switc...

[4]: MX blue nominal: http://www.wasdkeyboards.com/media/guide/graph-mx-blue.jpg

I remember upgrading the RAM from a paltry 128KB (i think). See all of those empty sockets?

Notably missing, and fair warning:

- Floppy controller

- Floppy drive! 5 1/4”

- Hard drive controller (RLL)

- CGA or Monochrome Display Adapter

- Serial port adapter if you want to modem (25-pin 16450 UART)

- PC-DOS

Good luck. These are harder than you think, have no sound but a “beep”, and can’t even keep the time between reboots.

upgrading the RAM from a paltry 128KB (i think).

Paltry? The original started with 16kB, and maxed out at 64 kB (after a ROM revision at 256kB)

have no sound but a “beep”

If you were willing to use most of the CPU for it, you could get (for the time) more than that beep out of it.

You could also make sound by toggling the relay that switched on/off the cassette motor :-)

Very good points! You’re right on all of them. I remember one game shop had a “RealSound” technology that sounded impressive for a PC speaker. Maybe “Mean Streets” was the name.

Mean Streets did in fact have digital audio samples that played out of the PC speaker, and it was a selling point highlighted on the box with a big red sticker: “Real Sound”.

Even if you can find a CGA or MDA, good luck finding a surviving monitor to display it.

Honestly, you're probably better off finding an intact PC on ebay or Craigslist or such.

And for doing anything practical, much better off with a Raspberry Pi variant.

Does it seem to you that literally anyone buying such a thing is concerned about practicality?

CGA is probably surprisingly easy. Composite out can plug into almost any TV made in the last 15 years, and many monitors. I could see using my Dell 2007FP for something like this; I've already tried it with a C128.

> Even if you can find a CGA or MDA, good luck finding a surviving monitor to display it.

A quick Google Shopping search finds plenty, as well as converter devices from those signals to VGA.

My parents still have a presumably functional CGA monitor in the basement because we’ve never thrown away any electronic we’ve owned. I am sure there are people like that out there.

Used, new old stock, and LCDs that support CGA/MDA/EGA are readily available. Converters from CGA/MDA to VGA are also readily available.

Most CGA cards had composite out, as CGA timings were based on TV standard.

with regard to displays, gbs-8200 will help here.

Gonbes GBS-8200/8220 CGA/EGA/YUV to VGA Arcade HD-Converter PCB allows all types of RGB, EGA, VGA or YUV component signals to be up-converter and display on a 31KHz PC VGA monitor, TFT monitor, LCD display, or HD-TV with VGA connection. No need to set dip switches in order to figure out the specific input frequency as all inputs are detected automatically! A great alternative to purchasing a expensive, heavy CGA monitor.

[0]: https://www.mikesarcade.com/cgi-bin/store.pl?sku=GBS-8200

The original IBM PC couldn't keep time between reboots either.

And a keyboard with a 5-pin DIN plug (not PS/2 or USB). Bonus points if the function keys go down the side and not across the top.

Does it include a cassette interface?

It does, but I don't believe it would be of much use, it was never really used on the original machines.

The "anonymous BIOS" is just begging to be replaced with a copy of the actual IBM BIOS (whose source code is also available), but I guess they decided not to supply it for copyright reasons; on the other hand, they did clone the hardware... I bet it raises all sorts of difficult questions for the IP lawyers.

IBM themselves released the board schematics for the 5150.

You wouldn't have a link, would you? I'd be interested in this...

http://www.minuszerodegrees.net/manuals/IBM_5150_Technical_R...

This is the technical manual for it

Thank you very much! Much obliged!

IBM also released the source for the BIOS - it’s still copyrighted.

In what year did they do that?

The same year the PC was released. The BIOS was listed in the tech reference manual appendix A.

http://classiccomputers.info/down/IBM/IBM_PC_5150/IBM_5150_T...

I recall it being part of the documentation that came with the original PCs.

> IBM published the entire listings of the BIOS for its original PC, PC XT, PC AT, and other contemporary PC models, in an appendix of the IBM PC Technical Reference Manual for each machine type.

https://en.wikipedia.org/wiki/BIOS

PC clones were deemed legal back in the day. No reason this wouldn't be.

Compaq created a new BIOS from a clean sheet of paper design, not a reverse engineered or ROM dump. The code of the BIOS on the PC and PC/XT were copyrighted.

I heard a tale - but can't find an online reference - for the first Compaq PC BIOS containing a bit that said 'Not (C) IBM' in order to pass some software checks searching for the strings '(C) IBM' being present at certain specific BIOS addresses.

Compaq wrote a specification based on IBM's published code listing. Then they handed it over to a separate team to reimplement.

userbinator's post clearly mentions cloning the hardware being problematic legality-wise and I was replying to that. Nobody's saying the cloned BIOS is problematic legal-wise.

What's the issue with cloning the hardware?

This is so very tempting, yet I know well I don't have the time or patience to set one of these up. I hope we'll at least see some of these pop up on YouTube, I'd love to watch someone assemble and use one of these.

And after you put it together, remember you need a power supply, a CGA? card and a keyboard to use it (and a DD or HD if you want to do anything besides looking at a screen)

I believe it was possible to use the original PC with cassette tapes instead of floppies, though you'd be limited to ROM BASIC in that case, and not PC-DOS.

There's a reason why DOS stands for Disk Operating System. :)

> There's a reason why DOS stands for Disk Operating System. :)

This is a retronym. Before purchased by Microsoft, DOS was developed by Seattle Computer Products under the name QDOS (Quick and Dirty Operating System). This was changed by Microsoft to MS-DOS with a changed meaning of "DOS".

Sure, that's correct. But the new name of "Disk OS" was completely relevant to this specific PC.

That's a pretty kit and that was a very large amount of work, congratulations on seeing it through. I suspect there is a larger market for a more complete offering, so maybe tackle a graphics board next?

I believe this video is about this project:

https://www.youtube.com/watch?v=fCe0I3RJajY

If you want to go the 'soft' route of emulation then there is this:

http://www.hampa.ch/pce/download.html

PCem is more accurate, supports more hardware and is easier to use.

http://pcem-emulator.co.uk/

Is this emulator ? https://youtu.be/Vg2n8Fp7F2g

Yes, though that seems to be a fork and not the official version.

I'm amused by the timing of this article. I just watched the anime series "Steins;Gate", and a major plot element revolves around getting a working 5150.

Steins;Gate undoubtedly got it from the John Titor urban legend.

I think that's a 5100-- almost a decade earlier and much more exotic.

I'm waiting for the full 3270 PC or the XT/370 kit.

Why don't they stuff the board? It would probably cost less than packaging the parts and dealing with customer service issues.

perhaps the

> Obviously, this is a project for an advanced electronic hobbyist and computer enthusiast.

is somewhat tongue-in-cheek: this could be the thing to get a kid who's already soldered together a bunch of (less expensive) analog hobby kits .. or the adult who's into that sort of thing.

it's pretty much the same thing as building model cars, airplanes, etc. although it doesn't teach you exactly how the thing works, the perceptual task of doing the soldering and checking out the traces gives some idea of how things piece together.

as far as vintage electronics go, IBM PCs (probably?) aren't that difficult to find for those who're essentially interested in abstracting away from the hardware.

DIY and hacked together out of third-party pieces? Yep, that's an authentic PC clone alright:)

I use the word "reproduction" because "clone" in the context of the Original IBM PC is/was an ill-defined word which means different things to different people:

https://en.wikipedia.org/wiki/IBM_PC_compatible

When some people think "clone", they think "compatibility" which leads to the following differences:

Excerpt:

"In May 1983, Future Computing defined four levels of compatibility:[11]

Operationally Compatible. Can run "the top selling" IBM PC software, use PC expansion boards, and read and write PC disks. Has "complementary features" like portability or lower price that distinguish computer from the PC, which is sold in the same store. Examples: (Best) Columbia Data Products, Compaq; (Better) Corona; (Good) Eagle.

Functionally Compatible. Runs own version of popular PC software. Cannot use PC expansion boards but can read and write PC disks. Cannot become Operationally Compatible. Example: TI Professional.

Data Compatible. May not run top PC software. Can read and/or write PC disks. Can become Functionally Compatible. Examples: NCR Decision Mate, Olivetti M20, Wang PC, Zenith Z-100.

Incompatible. Cannot read PC disks. Can become Data Compatible. Examples: Altos 586, DEC Rainbow 100, Grid Compass, Victor 9000."

So what type of a "clone" are we talking about?

I don't work for the company that makes the kit, and as far as I can tell prima facie, their kit is a faithful reproduction of the reference IBM PC hardware design.

I may be wrong, however.

Very shortly after this article was published nobody was using the term in any way but the top one (nor were less than 100% compatible PCs even sold for much longer).

My parents bought our first “ibm compatible” in 1987 and even back then the degree of compatibility was already a complete non-issue.

I'm not sure if you were alive at the time but an IBM PC "clone" was basically anything with even a hint of compatibility with PC software, no matter how half-assed. I think the usage of the word "reproduction" is perfectly acceptable here. :)

I am quite aware that the clones quickly became, in effect, the real thing. In spite of the way people apparently are interpreting, I meant my comment as a compliment; this system, in no small part because it is a clone, is perfectly in line with the original PC ecosystem.

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