Game Like it is 1983

The first computer I ever physically saw — I think — was an IBM System/3. You might not remember them. They were business computers for businesses that couldn’t justify a big mainframe. They were “midrange.” Nevermind that the thing probably had the memory and processing speed of the CPU inside my mouse. Time progressed and IBM moved on to the System/3x (for example, the System/32). Next up was the AS/400 and finally the IBM i, which is still in production. Here’s a secret, though, most of the code I’ve seen running on an IBM i dates back to at least the System/3 days and maybe even before that.

If you are interested in history, or midrange computers (which are mainframe-like in their operation), you might want to actually play with a real machine. A quick glance at eBay tells me that you might be able to get something workable for about $1000. Maybe. That’s a bit much. What if you could get time on one for free? Turns out, you can.

The Cloud Option

Head over to PUB400.com and register for an account. This won’t be instant — mine took a day or two. The system is for educational purposes, so be nice and don’t use it for commercial purposes. You get 150MB of storage (actually, some of the documentation says 250MB, and I have not tested it). While you are waiting for your account, you’ll need to grab a 5250 terminal emulator and adjust your thinking, unless you are a dyed-in-the-wool IBM guy.

Even though the IBM i looks like an old 1970’s midrange, the hardware is quite modern with a 64-bit CPU (and the architecture can handle 128 bits) and well-known stability. However, the interface is, well, nostalgic.

Ready…

Depending on your host computer, there are several IBM 5250 terminal programs available. They recommend tn5250 or tn5250j which use Java. However, I installed Mochasoft’s emulator into my Chrome browser. It is a 30-day free trial, but I figure in 30 days I’ll be over it, anyway.

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Homemade Computer from 1970s Chips

Sometimes it starts with a 555 timer and an op-amp. Other times with a small microcontroller. But the timing’s not so great and needs a dedicated timing crystal circuit. And maybe some more memory, and maybe the ATtiny should be swapped out for some 74LS-series chips. And now of course it needs video output too. Before you know it, you’re staring at a 40-chip computer that hearkens back to a simpler, yet somehow more complex, time of computing. At least that’s where [Marcel] is with his breadboard computer based on 1970s-era chips.

For what it does, this homebrew computer is relatively simple and straightforward. It gets 8 bits of processing power from 34 TTL chips. Another 6 round out the other features needed for the computer to operate. It is capable of rendering 64 colors in software and has more than enough memory for a computer of this sort. So far the only recurring problem [Marcel] has had has been with breadboard fatigue, as some of the chips keep popping out of the sockets.

This is a great project for anyone interested in homebrew or 8-bit computing, partially because of some of the self-imposed limitations that [Marcel] imposed on himself, like “only chips from the 70s”. It’s an impressive build on its own and looks to get much better since future plans call for a dedicated PCB to solve the issue with the worn-out breadboards. If you’re already invested in a project like this, don’t forget that the rabbit hole can go a little deeper: you can build a computer out of discrete transistors as well.

A Universal USB To Quadrature Encoder

Computer mice existed long before the Mac, and most of the old 8-bit computers had some software that could use a mouse. These mice had balls and quadrature encoders. While converters to turn these old mice into USB devices exist, going the other way isn’t so common. [Simon] has developed the answer to that problem in the form of SmallyMouse2. It turns a USB mouse into something that can be used with the BBC Micro, Acorn Master, Acorn Archimedes, Amiga, Atari ST and more.

The design of the SmallyMouse2 uses an AT90USB microcontroller that supports USB device and host mode, and allows for a few GPIOs. This microcontroller effectively converts a USB mouse into a BBC Micro user port AMX mouse, generic quadrature mouse, and a 10-pin expansion header. The firmware uses the LUFA USB stack, a common choice for these weird USB to retrocomputer projects.

The project is completely Open Source, and all the files to replicate this project from the KiCad project to the firmware are available on [Simon]’s GitHub. If you have one of these classic retrocomputers sitting in your attic, it might be a good time to check if you still have the mouse. If not, this is the perfect project to delve into to the classic GUIs of yesteryear.

Adding Character To The C64

The venerable Commodore 64, is there anything it can’t do? Like many 1980s computer platforms, direct access to memory and peripherals makes hacking easy and fun. In particular, you’ll find serial & parallel ports are ripe for experimentation, but the Commodore has its expansion/cartridge port, too, and [Frank Buss] decided to hook it up to a two-line character LCD.

Using the expansion port for this duty is a little unconventional. Unlike the parallel port, the expansion port doesn’t have a stable output, as such. The port contains the data lines of the 6510 CPU and thus updates whenever RAM is read or written to, rather then updating in a controlled fashion like a parallel port does. However, [Frank] found a way around this – the IO1 and IO2 lines go low when certain areas of memory are written to. By combining these with latch circuitry, it’s possible to gain up to 16 parallel output lines – more than enough to drive a simple HD44780 display! It’s a testament to the flexibility of 74-series logic.
It’s all built on a C64 cartridge proto-board of [Frank]’s own design, and effort was made to ensure the LCD works with BASIC for easy experimentation. It’s a tidy mod that could easily be built into a nice enclosure and perhaps used as the basis for an 8-bit automation project. Someone’s gotta top that Amiga 2000 running the school district HVAC, after all!

The Modern Retrocomputer: An Arduino Driven 6845 CRT Controller

[MmmmFloorPie] revived an old project to create the retro mashup of a 6845 CRT controller and a modern Arduino Uno. When it comes to chips, the Motorola 6845 is the great granddaddy of Cathode Ray Tube (CRT) interfaces. It was used in the IBM Monochrome display adapter, the Hercules graphics controller, CGA, Apple II terminal cards, and a host of other microcomputer and terminal systems.

Way back in 1989, [MmmmFloorPie] was a senior in college. His capstone project was a 68000 based computer which could record and playback audio, as well as display waveforms on a CRT. The CRT in question was ordered from a classified add in Popular Science magazine. It was a bare tube, so the heavy cardboard box it shipped in was repurposed as a case.

Fast forward to today, and  [MmmmFloorPie] wanted to power up his old project. The 68000 board was dead, and he wasn’t up to debugging the hundreds of point to point soldered connections. The CRT interface was a separate board including the 6845 and 32 KByte of RAM. It would only take a bit of hacking to bring that up. But what would replace the microprocessor?

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TI 99/4A Weather Station

If you still have a drawer full of slap bracelets from the 1990s because, you know, they might come back, then you’ll appreciate [Vorticon’s] latest project. Sure, we see lots of weather stations, but this one is controlled by a TI 99/4A computer. This home computer from the 1980s was actually ahead of its time with a 16-bit processor.

The sensors use Xbee modules and an Arduino Uno. Of course, the Uno has more power than the TI computer, but that’s not really the point, right? He’s made a series of videos detailing the construction (you can see the first one below, but there are five, so far).

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Vintage COSMAC Elf is Pretty Close to Original

Popular Electronics was famous for the article introducing the Altair 8800 back in 1975 (well, the cover date was 1975; it really came out in late 1974). That was so popular (no pun intended), that they ran more computer construction articles, including the SWTPC 680 late in 1975. But in 1976 a very popular article ran on building a very simple computer called the COSMAC ELF. [Youtubba] had an Altair, but always wanted a “cute” COSMAC ELF. Now, forty-something years later, he finally got around to it. He made the very detailed video about his experience, below.

Surprisingly, he didn’t have to look very hard for too many of the components as most of them were available from Digikey. He had to get compatible RAM chips, the 1802 CPU and LED displays. He also couldn’t find a look-alike crystal, so he used a fake one and a hidden oscillator. The result looks awfully close to the original. He even did a nice front panel using Front Panel Express.

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