The Z80 Membership Card (2015) | Hacker News Reader

The Z80 Membership Card (2015)

sunrise-ev.com

108 pointsexvi35 comments

I love the Z80, I started my career writing Z80 assembly for various embedded projects on a Z80 host system 45 years ago.

But you don't need a physical Z80 to enjoy that classic instruction set. For example see this source file from one of my projects; https://github.com/billforsternz/zargon/blob/main/src/zargon...

The good ole' Z80 assembly code is right there unaltered on the right, but it executes using C macros. In my humble consumer laptop I get a 40,000 times performance boost compared relative to a colleague's physical Z80 running the same code. I love the combination of nostalgia AND modern hardware performance.

This is beautiful. It's like C turned into a clearer and more usable language.

Seconding this opinion. That's some beautiful code and wonderful comments.

I grew up in a world where the Arduino already existed, but it was not until I tried building homebrew Z80 computers like this that I really felt I understood how computers/processors work at the low level.

Consider this a warning though: this hobby has caused me to involuntarily collect every model of Z80 powered TRS-80 computer.

If you wish to become hooked anyway, this project might be another good place to start: https://hackaday.io/project/159973-z80-mbc2-a-4-ics-homebrew...

I went through the exact same process, but with the 6502 (Ben Eater's videos, and then another SBC of my own design after). It's helped me become a better programmer too. Example: pointers in C now feel very natural instead of some abstract idea of "memory addresses, whatever those are".

And yep, I now also own many 6502 based computers :-)

I'm sure you already saw this, but in case others haven't: https://blondihacks.com/veronica/ is required reading for anyone into 6502. I was trying to rehabilitate a Cocktail Joust arcade cabinet I'd had in storage for years, and instead went off into a 6809 time warp for a while. Quinn's 6502 blog articles were helpful for inspiration while I breadboarded a really basic 6809 computer.

I ended up giving away the Joust machine to a guy (https://web.archive.org/web/20200709102945/http://www.robotr...) who had poured his heart and soul into Robotron disassembly and also was the Joust world-record holder in 1983, so I knew he'd appreciate it at least as much as I did. He happened to live in the area, and was more than happy to drive over and load it up. It's been 13 years since then. I hope he and it are doing well!

Factoid: It takes about six hours to reach 10 million points on Joust. Christian's record was 98 million points!

Not having my 'a-ha' moment with pointers until years into my education when doing assembly made me wonder why we don't start with a half-adder and work our way up from there instead of throwing novices right into C++ or Java OOP with no context.

That's how my comp sci degree went at Georgia Tech. There was a data structures and algorithms class first that used Java but then 2110 was building a computer from the (simulated) transistors up. I would've never understood pointers or C in general otherwise lol

Old greybeard here - I went the other way, learning 6502 assembler on an Apple II before I learned C. Having that 6502 experience when I first took a C class helped me immensely.

I think any kind of assembly experience is tremendously helpful in learning C. Assembly makes pointers and pointer arithmetic very intuitive, in my opinion.

Loved TRS-80 PCs and the COCO in early to mid 80's. My real first PC digital hardware class used those machines. Like most people in those days, could not really afford to purchase any but was gifted a COCO. w/ Editor/Assembler for experimentation :)

What I do not like is using a uC that is almost as capable as the whole board as part of it.

I know, you have to take a pragmatic approach… but feels like cheating… idk.

The Z80-MBC (the original breadboard version [0]) was actually the second Z80 computer I built. I first tried out one of the Grant Searle designs [1] on a breadboard, and it worked!... for literally 8 seconds, then the single ACIA chip I had waited weeks to get died for no reason. But I didn't have any way to debug what was wrong.

It also didn't help that I didn't have many EEPROMs or an EEPROM programmer at the time, but the ATMega32A can be programmed with an ordinary Arduino.

[0] - https://hackaday.io/project/19000-a-4-4ics-z80-homemade-comp...

[1] - http://searle.x10host.com/z80/SimpleZ80.html

I have very sadly done the same with ZX Spectrums but the quest is never ending due to all of the baltic clones

Same here but Oric-1/Atmos.

There's also an 1802 Membership Card—which I knew as the COSMAC Elf Membership Card [1][2]. Switches and LEDs. I built one of these kits a decade ago but mine didn't work. (I still need to pull it out and try to debug it. For all I know I did assemble it correctly and there is just a RUN switch or something I did not know to flip.)

[1] http://www.sunrise-ev.com/1802.htm

[2] http://www.cosmacelf.com/gallery/membership-cards/

Nice, I clicked to see if anybody had mentioned "the original." I built one of those as well. It is a very cute little system, and the 1802 is simple enough that the little front panel is a somewhat usable interface.

Here's some context on the RCA 1802 (COSMAC) Membership Card, also by Lee Hart at the same website, which is the real star of the lineup:

http://www.retrotechnology.com/memship/memship.html

Nice to see old tech revitalised - I had fun with the Australian version of a Z80 single board computer - https://en.wikipedia.org/wiki/TEC-1

Love the Freak Brothers references; two US counter cultures that do cross pollinate. Z80MC RAM & ROM seem v generous compared to the ZX81 I used to cut my asm teeth, wobbly RAM pack and all...

Looks like the caption to the image references a "Creative Computing" cover from 1979—so an indirect FFFBrothers reference.

It's a shame Zilog stopped making Z80s. Presumably this means you can't make one of these from new components any more. Perhaps someone could create a new iteration of the same idea.

The Z80 instruction set lives on via the eZ80, Z180 and others which are binary compatible with the original Z80 instruction set. Unfortunately Zilog stopped making the 40 pin DIP package a couple years ago so yeah this specific board will be hard to source. You can still find them on gray market, mostly ones that have been desoldered from existing boards.

Even if you made a version of this board with the footprint changed to the QFP eZ80, it probably wouldn't work because the eZ80 has different memory mapping and clocking differences.

The Z180 has however had its PLCC packages discontinued. Personally, I find SMD CPUs to not be appealing for these sorts of projects, even if the Z180 is a great chip.

The Z80 is still used in consumer products. TI-80/TI-83 calculators are a well known example.

For the aspiring hacker, we've also got:

The 80's/90's VeriFone Tranz 330 credit card terminal, which has a complete Z80 computer inside with DART, CTC and PIO chips, 32K RAM, and a socketed EPROM.

The Cidco Mailstation, which has a Z80, sizable monochrome LCD, and full-ish size keyboard, perfect to hack into a TRS-80 Model 100 style laptop.

You can pick up either on Ebay right now for ~$25

You can probably put together something similar with A-Z80 [0] or a similar FPGA redesign.

[0] https://github.com/gdevic/A-Z80

Luckily so many were made, they will be around for a while yet. For years now you've been able to buy (recycled?) ones on Ebay or Aliexpress, and at a price much cheaper than the new ones sold for.

It will probably be a decade or longer until those sources start to dry up, but even at that the Z80 will never become as rare as say, a SID chip.

My first computer was a Z80. It was an Amstrad 8256, also known as the Joyce. It was sold as a word processor, but it came with a copy of cp/m you could load in. I bought it because it was about as powerful as the Apple computer of the time, but at half the price. That was a great little computer.

I think this is very cool, even though I have no historical connection to the Z80 it's of course a well-regarded and firmly entrenched/popular retro CPU.

But this really is a stretch:

The Z80 Membership Card itself is a stand-alone single-board computer that can "power up" your projects, like the Parallax BASIC Stamps or Arduino microcomputers.

Both of those are very commonly called microcontrollers, not microcomputers, since they have all of those extra chips merged into the single package of the CPU.

Take a look at the Arduino Uno [1] which is a very typical (if old) example: you will see that the board is not covered in ICs from edge to edge, since all of the main functionality is in the single-chip microcontroller. I think the second big-ish package visible is for the USB, but that also disappears on more modern controllers with on-board support for USB.

[1]: https://en.wikipedia.org/wiki/Arduino_Uno#/media/File:Arduin...

It’s pretty clear that the design of the Z80 Membership Card is intentionally steered towards the micro-computer ethos. The distinction between a microcomputer and a microcontroller is a subtle one; in fact, it’s up to the use-case whether either term is applicable. Microcontrollers do, indeed, provide lots of I/O and rudimentary computation capabilities - whereas Microcomputers have computing power, of a sort, and some facility for I/O which may - or may not be - expansive.

So the stretch is not much more than a matter of semantics, imho. I’ve used Z80’s as microcontrollers, I’ve also used them as microcomputers.

This is pretty eye-opening. It really drives home how simple the core control logic can be. Starting with toy cars or small-scale vehicles feels like a great way to teach and validate these ideas before layering on unnecessary complexity.

Very cool. My version of this years back was a TI-83+ I learned asm on.

Spot on, programming on any of these TI calculators in either BASIC or ASM is a great way to learn programming and can really teach a programmer a lot about how computers work, and how to program efficiently. I still think that TI calculators could play an important role in computer science education. If you haven't checked it out already check out the Cosmac Elf memebership card and some of the Homebrew 1802 software and hardware, there is a lot of nice stuff.

fwiw, I have two Z80s--maybe more--in a box among all my other parts.

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The Z80 Mem­ber­ship Card (2015)

The Z80 Membership Card (2015)