The 1980s called – asking for the Z80 Membership Card

The ’80’s and early ’90’s saw a huge proliferation of “personal” computers, spawning an army of hacker kids who would go on to hone their computing chops on 8-bit and 16-bit computers from brands such as Sinclair, Commodore, Acorn, Apple, Atari, Tandy/RadioShack and Texas Instruments. Fast forward to 2017, and Raspberry-Pi, BeagleBone and micro:bit computers reign supreme. But the old 8-bit and 16-bit computer systems can still teach us a lot.

[Lee Hart] has built the amazing Z80 Membership Card — a Z80 computer that fits in an Altoids tin. His design uses generic through hole parts mounted on a PCB with large pads, thick tracks and lots of track clearances, making assembly easy. Add to this his detailed documentation, where he weaves some amazing story telling, and it makes for a really enjoyable, nostalgic build. It makes you want to get under the hood and learn about computers all over again. The Z80 Membership Card features a Zilog Z80 microprocessor running at 4 MHz with 32k RAM and 32K EPROM, loaded with BASIC interpreter and monitor programs. A pair of 30-pin headers provide connections to power, I/O pins, data, address and control signals.

To accompany this board, he’s built a couple of companion “shield” boards. The Front Panel Card has a 16-key hex pad, 7-digit 7-segment LED display and Serial port. [Lee] has packed in a ton of features on the custom monitor ROM for the front panel card making it a versatile, two board, 8-bit system. Recently, he finished testing a third board in this series — a Serial/SD-Card/RAM shield which adds bank-switchable RAM and SD-card interface to provide “disk” storage. He’s managed to run a full CP/M-80 operating system on it using 64k of RAM. The two-board stack fits nicely in a regular Altoids tin. A fellow hacker who built the three-board sandwich found it too tall for the Altoids tin, and shared the design for a 3D printable enclosure.

[Lee] provides detailed documentation about the project on his blog with schematics, assembly instructions and code. He’s happy to answer questions from anyone who wants help building this computer. Do check out all of his other projects, a couple of which we’ve covered in the past. Check out Lee Hart’s Membership Card — a similar Altoids tin sized tribute to the 1802 CMOS chip and how he’s Anthropomorphizing Microprocessors.

Finally, we have to stress this once again — check out his Assembly Manuals [PDF, exhibit #1] — they are amazingly entertaining.

Thanks to [Matthew Kelley] who grabbed one of [Lee]’s kits and then tipped us off.

Integrated Circuit Reverse Engineering, 1970s Style

We are used to stories about reverse engineering integrated circuits, in these pages. Some fascinating exposés of classic chips have been produced by people such as the ever-hard-working [Ken Shirriff].

You might think that this practice would be something new, confined only to those interested in the workings of now-obsolete silicon. But the secrets of these chips were closely guarded commercial intelligence back in the day, and there was a small industry of experts whose living came from unlocking them.

Electron micrograph of a wire bond to the Z80 CTC die
Electron micrograph of a wire bond to the Z80 CTC die

Integrated Circuit Engineering Corporation were a Scottsdale, Arizona based company who specialised in semiconductor industry data. They have long since been swallowed up in a series of corporate takeovers, but we have a fascinating window into their activities because their archive is preserved by the Smithsonian Institution. They reverse engineered integrated circuits to produce reports containing detailed information about their mechanical properties as well as their operation, and just such a report is our subject today. Their 1979 examination of the Zilog Z80 CTC (PDF) starts with an examination of the package, in this case the more expensive ceramic variant, then looks in detail at the internal construction of the die itself, and its bonding wires. We are then taken in its typewritten pages through an extensive analysis of the circuitry on the die, with gate-level circuits to explain the operation of each part.

The detail contained in this report is extraordinary, it is clear that a huge amount of work went into its production and it would have been of huge value to certain of Zilog’s customers and competitors. At the time this would have been extremely commercially sensitive information, even if it now seems like a historical curiosity.

The Z80 CTC is a 4-channel counter/timer peripheral chip for the wildly succesful Z80 8-bit microprocessor, in a 28-pin dual-in-line package. We were surprised to find from a quick search that you can still buy this chip from some of the usual suppliers rather than the surplus houses, so it may even still be in production.

If IC reverse engineering takes your fancy, take a look at our archive of [Ken Shirriff] posts.

Thanks [fortytwo] for the tip.

Easy to build Z80 single board computer

[Alexis] sent in a single board computer he’s been working on. The project goal of his build was making it easily reproducible. From looking at the schematics, it’s one of the simplest fully-functional computers we’ve seen. The build runs CP/M 2.2 off of two 3.5 inch floppies. This opens up a lot of options as to what software is already available. Although it operates over a serial terminal, [Alexis] pretty much duplicated an Osborne I, only at double the speed.

[Alexis] got a little e-fame from his earlier 8088 homebrew computer built from very early 8088’s rescued from an electronics junk shop. These 8088 computers made the blog rounds by playing Still Alive with a SID chip from a Commodore 64 and a YM2151 FM synth chip.

For now, I guess we’ll have to settle for a video of [Alexis]’ Z80 computer running CP/M. Check out a video after the break of his computer running the greatest Infocom adventure, Hitchhiker’s Guide to the Galaxy.

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Meet Mr. Clappidoo


[Laurence] tinkers around the house quite a bit, making all sorts of fun interactive toys for his children to play with. Mr. Clappidoo is a toy that he finished a while back, which bears a striking resemblance to one of his projects we recently showed you, Papydoo. This is not a coincidence, as Papydoo was created after Mr. Clappidoo was built, borrowing many features from his predecessor.

Who is your daddy and what does he do?

It’s a good thing you asked. Mr. Clappidoo uses an IR motion sensor to detect nearby objects, waking up and interacting with whatever crosses his path. He is capable of four different random moods ranging from angry to flirty. He projects these moods by changing the color of his LED-lit eyes as well as playing simple sounds. A balsa wood chest makes up Clappidoo’s body, and he repeatedly claps his lid mouth open and shut using a small servo, hence the name.

Like his other projects, [Lawrence] has focused his efforts to ensure that the three AA batteries used to power Clappidoo last as long as possible. He says that with moderate usage the device can run off the same set of batteries for a few months before needing replacement.

It’s a fun little contraption, sure to please the kids. Stick around for a quick video of Clappidoo in action.

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V4Z80P: The 8-bit laptop

[Phil] over at Retroleum has cobbled together a clean, well put together laptop based entirely around a Zilog Z80 microprocessor and a pair of Spartan II FPGAs. These FPGAs allow him to reduce the number of devices on his board, and therefore cut his production cost as well as device size. He even managed to integrate a salvaged PSOne screen. The laptop comes complete with [Phil]’s own Homebrew OS as well as a great graphical vector based demo.

Sure he’s updated the project in recent years to shrink the board, speeding up the Z80, and increasing the peripheral speed and functionality, but we’re suckers here for a total package hack. Seriously though, check out the newest version of the device as well as the backlog that shows the project growing over time.

Thanks to [Steth] for the heads up.

Zilog in a matchbox

Now you can have a Zilog computer in the form factor of a matchbox. The RamBlade is a tiny PCB that uses a Parallax Propeller IC to implement the CP/M language. The OS is stored on a microSD card, with a four-pin serial interface (3V3, GND, SO, SI) that allows operation via a terminal program.

Smaller and more resilient than building your own from ancient logic chips, we see this a way to get a whole new set of people interested in this old technology.

[Thanks Oldbitcollector]

Proto-board Z80 computer


We’ve seen  Z80 processor based computers before but they usually use a printed circuit board to easily and reliably connect all the components. [Marton] sent us his Z80 based computer from a while back that is built entirely on prototyping board. He made his own video board that utilizes a TV as the monitor and his own mainboard incorporating a keyboard controller. The system runs at 4 MHz, has 32k of ram, and runs [Marton’s] own system software which he has posted. Its quite impressive and we love the protoboard porn with thousands of grey wires running everywhere.

[Marton] used the resources on [Hans Summers’] site for his project. Make sure to check it out if you’re interested in a broader background concerning DIY Zilog Z80 computers.