[Plasmode] has created several Z80-compatible board designs, at least four of them using the oddball Z280. The Z280 was a special variant of a Z80 that could bootstrap itself with no external PROM, making it ideal for anyone trying to build a system on a breadboard. According to his post, the cost to build the board is about $35.
Although the 8080 CPU got a lot of glory, it was much harder to use than the Zilog Z80. The Z80 only required a single clock and power supply, so it was much easier to build a system, even on a breadboard. On top of that, the bus wasn’t multiplexed and it could refresh DRAM memory by itself. Maybe that’s why you can still get Z80-derived chips readily. There was one thing, though, you needed an EPROM or some other way to run some initial code to bootstrap your system. Zilog knew this was a problem. In those days, you had to use a special tool to burn a PROM and, unless it was erasable and you had the special UV light to erase it, any mistakes cost you a chip.
Continue reading “This Z80 Computer Bootstraps Itself”
If you wanted me to demo CP/M running on an emulated Altair 8800, I’d pull out a tiny board from my pocket. You might wonder how I wound up with an Altair 8800 that runs CP/M (even WordStar), that fits in your pocket and cost less than $10. Turns out it’s a story that goes back to 1975.
When the Altair 8800 arrived back in 1975, I wanted one. Badly. I’d been reading about computers but had no hands-on experience. But back then, as far as I was concerned, the $400 price tag might as well have been a million bucks. I was working for no real pay in my family’s store, though in all fairness, adjusted into today’s money that was about $2,000.
I’d love to buy one now, but a real Altair costs even more today than it did back then. They also take up a lot of desk space. Sure, there are replicas and I’ve had a few. I even helped work the kinks out of Vince Briel’s clone which I’ve enjoyed. However, the Briel computer has two problems. First, it takes a little work to drive a serial port (it uses a VGA and a PS/2 keyboard). Second, while it’s smaller than a real Altair, it is still pretty large — a byproduct of its beautiful front panel.
So to quickly show off CP/M to someone, you need to haul out a big box and find a VGA monitor and PS/2 keyboard — both of which are becoming vanishing commodities. I made some modifications to get the serial port working, but it is still a lot to cart around. You could go the software route with a simulator like SIMH or Z80pack, but now instead of finding a VGA monitor and a PS/2 keyboard, you need to find a computer where you can install the software. What I really wanted was a simple and portable device that could boot CP/M.
Continue reading “ESP32 Altair Emulator Gets Split Personality”
If you want to run an old CP/M program — maybe you want to run WordStar or play StarTrek — you have several options. One is to acquire some classic hardware. You can also build a new computer using a Z80 or some other processor that will emulate a Z80. Finally, you can emulate old hardware on your current computer. The iz-cpm project from [ivanizag] takes this last approach. Unlike some emulators, iz-cpm doesn’t try to emulate everything in one simulated environment. Instead, it directly accesses your file system so it allows CP/M executables to run more as though they were a native program.
You can think of it as Wine for CP/M. The code is portable to Linux, Windows, or MacOS. The author mentions, though, that it won’t run on CP/M itself! The program can run an executable standalone which means you could set .COM files up to execute automatically if you wanted to.
Continue reading “Portable CP/M Runs The Classics Anywhere”
We begin with sad news indeed as we mark the passing of Marcel van Kervinck on Monday. The name might not ring a bell, but his project, the Gigatron TTL computer, certainly will. We did a deep dive on the microprocessor-less computer a while back, and Marcel was a regular at conferences and on the Gigatron forums, supporting users and extending what the computer can do. He was pretty candid about his health issues, and I’ll add that when I approached him a few weeks ago out of the blue about perhaps doing a Hack Chat about Gigatron, he was brutally honest about how little time he had left and that he wouldn’t make it that long. I was blown away by the grace and courage he displayed. His co-conspirator Walter Belger will carry on the Gigatron mission, including joining us for a Hack Chat on June 24. In the meantime, this might be a great time to pick up a Gigatron kit before they’re all sold out and get busy soldering all those delicious through-hole TTL chips.
May of 2020 is the month that never seems to end, and as the world’s focus seems to shift away from the immediate public health aspects of the ongoing COVID-19 pandemic to the long-term economic impact of the response to it, we happened across a very interesting article on just that topic. Mike Robbins from the Circuit Lab has modeled the economic impact of the pandemic using analog circuit simulations. He models people as charges and the flow of people between diseases states as currents; the model has capacitors to store the charge and allow him to measure voltages and filters that model the time delays needed for public policy changes to be adopted. It’s a fascinating mashup of engineering and policy. You can play with the model online, tweak parameters, and see what you come up with.
One of the things that the above model makes clear is that waiting to fully reopen the economy until a vaccine is ready is a long and dangerous game. But there has at least been some progress on that front, as Massachusetts biotech firm Moderna announced success in Phase 1 clinical trials of its novel mRNA vaccine against SARS-CoV-2. It’s important to temper expectations here; Phase 1 trials are only the beginning of human testing, aimed at determining the highest treatment dose that won’t cause serious side effects. Phase 2 and Phase 3 trials are much more involved, so there’s a long way to go before the vaccine, mRNA-1273, is ready for use. If you need to brush up on how these new vaccines work, check out our handy guide to mRNA vaccines.
In happier news, the “moar memory” version of the Raspberry Pi 4 is now on sale. Eben Upton announced that the 8GB version of the Pi 4 is now available for $75. The upgrade was apparently delayed by the lack of an 8GB LPDDR SDRAM chip in a package that would work in the Pi manufacturing process. They’ve also released a beta of a 64-bit version of the Raspberry Pi OS, if you’re interested in a bleeding-edge flex.
And finally, for those who missed the first wave of the computer revolution and never had a blinkenlight machine, you can at least partially scratch that itch with this Internet-connected Altair 8800. Jesse Downing has written a queueing system that allows users to connect to the machine via ssh and use Microsoft BASIC 5.0 on CP/M. Need to see those glorious front panels lights do their thing? Jesse has kindly set up a live stream for that, with an overlay of the current console output. It’s a great way to relive your misspent youth, or to get a taste of what computing was like when soldering skills were a barrier to entry.
When life hands you a ridiculously expensive and massively powerful FPGA dev board, your first reaction may not be to build a 16-core Z80 laptop with it. If it’s not, perhaps you should examine your priorities, because that’s what [Chris Fenton] did, with the result being the wonderfully impractical “ZedRipper.”
Our first impression is that we’ve got to start hanging around a better class of lab, because [Chris] came by this $6000 FPGA board as the result of a lab cleanout; the best we ever scored was a few old Cat-5 cables and some power strips. The Stratix FPGA formed the heart of the design, surrounded by a few breakout boards for the 10.1″ VGA display and the keyboard, which was salvaged from an old PS/2. The 16 Z80 cores running in the FPGA are connected by a ring-topology network, which [Chris] dubs the “Z-Ring”. One of the Z80 cores, the server core, runs CP/M 2.2 and a file server called CP/NET, while the other fifteen machines are clients that run CP/NOS. A simple window manager shows 80 x 25 character terminal sessions for the server and any three of the clients at once, and the whole thing, including a LiPo battery pack, fits into a laser-cut plywood case. It’s retro, it’s modern, it’s overkill, and we absolutely love it.
Reading over [Chris]’s build log puts us in the mood to break out our 2019 Superconference badge and try spinning up a Z80 of our own. If you decide to hack the FPGA-est of conference badges, you might want to check out what [Sprite_TM] has to say about it. After all, he designed it. And you’ll certainly want to look at some of the awesome badge hacks we saw at Supercon.
Thanks to [yNos] for the tip.
Fun fact, the Osborne 1 debuted with a price tag equivalent to about $5,000 in today’s value. With a gigantic 9″ screen and twin floppy drives (for making mix tapes, right?) the real miracle of the machine was its portability, something unheard of at the time. The retrocomputing trend is to lovingly and carefully restore these old machines to their former glory, regardless of how clunky or underpowered they are by modern standards. But sometimes they can’t be saved yet it’s still possible to gut and rebuild the machine with modern hardware, like with this Raspberry Pi used to revive an Osborne 1.
Purists will turn their nose up at this one, and we admit that this one feels a little like “restoring” radios from the 30s by chucking out the original chassis and throwing in a streaming player. But [koff1979] went to a lot of effort to keep the original Osborne look and feel in the final product. We imagine that with the original guts replaced by a Pi and a small LCD display taking the place of the 80 character by 24 line CRT, the machine is less strain on the shoulder when carrying it around. (We hear the original Osborne 1 was portable in the same way that an anvil is technically portable.) The Pi runs an emulator to get the original CP/M experience; it even runs Wordstar. The tricky part about this build was making the original keyboard talk to the Pi, which was accomplished with an Arduino that translates key presses to USB.
As an aside, if reading this has given you a twinge of nostalgia and you’re on the Eastern seaboard you may want to check out more vintage gear at the VCF East this weekend. If you hail from Europe, get your hack on with CP/M and a retrocomputing badge at Hackaday Belgrade one wee from now.
We’ve seen the Raspberry Pi pressed into retrocomputing duty before, of course. Here’s one used to emulate a Commodore 1541 disk drive, and another in the laptop Clive Sinclair never built.
Continue reading “Suitcase Computer Reborn With Raspberry Pi Inside”
These days, a good proxy for hacking prowess is getting Doom playable on the oldest piece of hardware imaginable. While we respect and applaud these efforts, perhaps the bar should be set a bit higher. Like orbital mechanics on an early 80s Kaypro, perhaps?
At least that’s the hurdle [Chris Fenton] set for himself as a fun project for his spare time with his Kaypro 2/84, a vintage Z80 clocking in at a screaming 4 MHz and 64-kB of RAM. With its built-in 80×25, 9″ green phosphor CRT monitor and flip-top keyboard, the Kaypro fit into that loveable luggable category of machines and predated IBM’s and Apple’s market dominance by a few years. The CP/M operating system has actually aged pretty well — but well enough to port [Chris]’ Deep Dish Nine, a graphical game written for the Arduboy that uses Kerbal-like orbital mechanics skills to deliver interplanetary pizzas? In the first instance, no — the game, ported to Turbo Pascal, only managed fractional frames per second, rendering it unplayable. But with some very clever coding, [Chris] was able to improve refresh rates 10-fold. The optimization road not taken includes hardware hacks, like overclocking the Z80 or even replacing it with an FPGA and emulator, but that’s hardly keeping with the spirit of the thing.
It’s always great to see vintage machines pushing the envelope. A great place to see them is one of the Vintage Computer Fairs, like the upcoming VCF Southeast in Georgia. We were at the one diagonally across the country a few weeks back, and they’re well worth the trip.