HDMI For The Color Computer 2

[Scott Baker] bought a TRS-80 Color Computer off eBay some five years ago. He’d always intended to add a CoCoVGA or CoCoDV upgrade to hook it up to a monitor, but the device was sold out and his name never made it off the waitlist. Thus, he decided to build his own solution to give the classic machine a proper HDMI output.

The concept behind the project is simple enough—grab the digital signals that feed the MC6847 IC responsible for generating the analog video output, and use them to create an all-digital video output over HDMI. [Scott] achieved this by using a Tang Nano board, which hosts a Gowin GW1N-1 FPGA. It’s able to snoop the signals heading to the MC6847 and, with some supporting components and level shifters, it can spit out video befitting modern screens. To make the system nicely complete, an analog-to-digital converter is also included to pick up the analog sound output from the TRS-80 and spit it out down the same HDMI cable. Such convenience!

There’s something strangely anachronistic about grabbing a TRS-80 off the shelf and hooking it up to a flatscreen with a single HDMI cable. Regardless, it’s a pretty great way to play with your old machine without having to futz with heavy old CRTs. We’ve featured plenty of similar projects before, too. Continue reading “HDMI For The Color Computer 2” →

The World’s First GPIB Speech Synthesizer, And It’s For A GRiD Compass

The GRiD Compass is a legendary portable computer — a taste of an early-80s future with bubble memory, tough enough for NASA to take them into space, and one of the machines which defined the beginnings of the form factor we know today as a laptop. They’re not easy to come by, but [Scott M. Baker] got his hands on one. As well as nursing it back to health, he’s made an unusual peripheral, a GPIB speech synthesizer.

The GRiD arrived in one piece despite sketchy packaging, and after a little confusion over its line voltage it ran as well as the day it was made. It was designed to use GPIB as its interface for large peripherals such as printers or disk drives, so it was that interface picked for the speech synthesizer. It emulates a GPIB printer, and bytes are sent to the synthesizer chip by printing to LPT1, making driving it an easy process.

The synth itself is a clever design that allows the use of all the various speech chips of the day. It achieves this using a GPIB carrier board holding the interfacing, and a set of plug-in modules, one for each different chip. It’s certainly an unusual peripheral.

You can see more details in the video below the break, meanwhile if you can’t get the real thing there’s a cyberdeck tribute you can make.

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Who Had “New OS For The Z80” On Their 2026 Bingo Card?

Some might say the venerable Z80 doesn’t need another operating system, but [Scott Baker] obviously disagrees. He has come up with a brand new, from scratch OS called NostOS for the Z80-based RC2014 homebrew retrocomputer. [Scott] describes it as CP/M-like, but it’s not CP/M– in fact, it’s totally incompatible with CP/M–and has a few tricks of its own up its sleeve.

As you might expect of an operating system for this vintage of hardware, it is “rommable” — that is, designed to run from read-only-memory, and fit inside 64kB. It of course supports banking memory to go higher than that 16 bit limit, and natively supports common serial devices, along with the good old WD37C65 floppy controller to get some spinning rust into the game. Of course if you don’t have floppies you can plug in a compact flash card– try that with CP/M– or, interestingly Intel Bubble Memory. [Scott] has a soft-spot for bubble memory, which at one point seemed poised to replace both hard drives and RAM at the same time. We also appreciate that he included drivers for vacuum fluorescent displays, another forgotten but very cool technology. Back in the day, this operating system would have enabled a very cool little computer, especially when you take his implementation of text-to-speech with the SP0256A-AL2 chip. Fancy a game of talking Zork? Yes, he ported Zork, and yes, it talks.

The whole thing is, of course, open-source, and available on [Scott]’s GitHub. Unlike too many open-source projects, the documentation is top-notch, to the point that we could picture getting it in a three-ring binder with a 5 1/4 floppy on the inside cover. If you like video, we’ve embedded [Scott]’s walkthrough but his blog and the docs on GitHub have everything there and more if you’re not into rapidly-flickering-pixels as an information exchange medium.

[Scott] isn’t wedded to Zilog, for the record; this OS should run on an Intel 8080, perhaps like the one in the Prompt 80 he restored last year. 

Thanks to [Scott Baker] for the tip!

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Scott holding the demo board which has a 7-segment display and keyboard attached

4-bit Single Board Computer Based On The Intel 4004 Microprocessor

[Scott Baker] is at it again and this time he has built a 4-bit single board computer based on the Intel 4004 microprocessor.

In the board design [Scott] covers the CPU (both the Intel 4004 and 4040 are supported), and its support chips: the 4201A clock-generator, its crystal, and the 4289 Standard Memory Interface. The 4289 irons out the 4-bit interface for use with 8-bit ROMs. Included is a ATF22V10 PLD for miscellaneous logic, a 74HCT138 for chip-select, and a bunch of inverters for TTL compatibility (the 4004 itself uses 15 V logic with +5 V Vss and -10 V Vdd).

[Scott] goes on to discuss the power supply, ROM and page mapper, the serial interface, the RC2014 bus interface, RAM, and the multimodule interface. Then comes the implementation, a very tidy custom PCB populated with a bunch of integrated circuits, some passive components, a handful of LEDs, and a few I/O ports. [Scott] credits Jim Loo’s Intel 4004 SBC project as the genesis of his own build.

If you’re interested in seeing this board put to work check out the video embedded below. If you’d like to know more about the 4004 be sure to check out Supersize Your Intel 4004 By Over 10 Times, The 4004 Upgrade You’ve Been Waiting For, and Calculating Pi On The 4004 CPU, Intel’s First Microprocessor.

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A photo of two magnetic bubble memories installed in a circuit board

Scott Baker’s Magnetic Bubble Memory Mega-Post

Over on his blog our hacker [Scott Baker] has a Magnetic Bubble Memory Mega-Post.

If you haven’t heard of magnetic bubble memory before it’s basically obsolete nonvolatile memory. Since the 1970s when it was introduced this type of memory has been outperformed in every dimension including durability, reliability, price, density, performance, and so on. For any given application of bubble memory you will be able to find an alternative technology which is better in many ways. Except if you want some old tech to geek out over, in that case magnetic bubble memory is for you!

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Scott and his Prompt 80

Restoring A Vintage Intel Prompt 80 8080 Microcomputer Trainer

Over on his blog our hacker [Scott Baker] restores a Prompt 80, which was a development system for the 8-bit Intel 8080 CPU.

[Scott] acquired this broken trainer on eBay and then set about restoring it. The trainer provides I/O for programming, probing, and debugging an attached CPU. The first problem discovered when opening the case is that the CPU board is missing. The original board was an 80/10 but [Scott] ended up installing a newer 80/10A board he scored for fifty bucks. Later he upgraded to an 80/10B which increased the RAM and added a multimodule slot.

[Scott] has some luck fixing the failed power supply by recapping some of the smaller electrolytic capacitors which were showing high ESR. Once he had the board installed and the power supply functional he was able to input his first assembly program: a Cylon LED program! Making artistic use of the LEDs attached to the parallel port. You can see the results in the video embedded below.

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An Intel 8008 On A Single-Board Computer

The last time we covered [Dr. Scott M. Baker], he made his Heathkit H8 run on a considerably older processor than it was made for. This time, apparently still not satisfied with the number of 8008 computers, he made an Intel 8008-based single-board computer.

The Mini-08, as [Scott] calls it, is based on his previous endeavour of downgrading the Heathkit H8. Its “CPU board” has even more memory than its predecessor at 128KiB RAM and ROM and an 8251 UART connected to a DB25 serial port. The entirely optional “display board” adds to that 10 digits of 7-segment displays, a backlit Cherry MX Blue hexadecimal keypad, a real-time clock and even a 4-voice sound generator!

[Scott] has also done an impressive job with the software, porting BASIC, FORTH, a clone of Star Trek and some utilities to his Mini-08. He demonstrates both BASIC and FORTH by printing “SCOTT WAS HERE” in a for loop and finishes off by showing how to use some of the display board with FORTH.

Like last time, he published design files and resources for you to enjoy. Overall, an interesting spin on the retro single-board computer concept.

Video after the break.

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