Retrocomputing

1584 Articles

A Lambda 8300 Lives Again

December 10, 2020 by 3 Comments

If you follow retrocomputing — or you are simply old enough to remember those days — you hear the same names over and over. Commodore, Apple, Radio Shack, and Sinclair, for example. But what about the Lambda 8300? Most people haven’t heard of these but [Mike] has and he has quite a few of them. The computer is similar to a Sinclair ZX81, but not an exact clone. All of his machines need some repairs (he’s promised repair videos are on their way), but for the video below he wired a monitor directly to the PCB to get steady output, so apparently the RF modulator is the failing subsystem in this case.

Once the video cleared up, you can see a walkthrough of running a simple BASIC program. As was common in those days, the computer used an audio cassette recorder for data storage. [Mike] picked up some dedicated recorders meant for computer use, but neither were in working shape. However, a consumer player works fine.

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PET 2001 Emulator On $2 Of Hardware

December 9, 2020 by 20 Comments

Since the late 60s, Moore’s law has predicted with precision that the number of semiconductors that will fit on a chip about doubles every two years. While this means more and more powerful computers, every year, it also means that old computers can be built on smaller and cheaper hardware. This project from [Bjoern] shows just how small, too, as he squeezes a PET 2001 onto the STM32 Blue Pill.

While the PET 2001 was an interesting computer built by Commodore this project wasn’t meant to be a faithful recreation, but rather to test the video output of the Blue Pill, with the PET emulation a secondary goal. It outputs a composite video signal which takes up a good bit of processing power, but the PET emulation still works, although it is slightly slow and isn’t optimized perfectly. [Bjoern] also wired up a working keyboard matrix as well although missed a few wire placements and made up for it in the software.

With his own home-brew software running on the $2 board, he has something interesting to display over his composite video output. While we can’t say we’d emulate an entire PC just to get experience with composite video, we’re happy to see someone did. If you’d like to see a more faithful recreation of this quirky piece of computing history, we’ve got that covered as well.

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A Portable Serial Terminal That Should Be From The 1970s

December 8, 2020 by 38 Comments

The humble standalone serial terminal might be long gone from the collective computing experience, but in the ghostly form of a software virtual terminal and a serial converter it remains the most basic fall-back and essential tool of the computer hardware hacker. [Mitsuru Yamada] has created the product that should have been made in the serial terminal’s heyday, a standalone handheld terminal using a 6809 microprocessor and vintage HP dot matrix LEDs. In a die-cast box with full push-button keyboard it’s entirely ready to roll up to a DB-25 wall socket and log into the PDP/11 in the basement.

Using today’s parts we might achieve the same feat with a single-chip microcontroller and a small LCD or OLED panel, but with an older microcomputer there is more system-building required. The 6809 is a wise choice from the 1970s arsenal because it has some on-board RAM, thus there’s no need for a RAM chip. Thus the whole thing is achieved with only a 2716 EPROM for the software, a 6850 UART with MAX232 driver  for the serial port, and a few 74 chips for glue logic, chip selects, and I/O ports to handle keyboard and display. There’s no battery in the case, but no doubt that could be easily accommodated. Also there’s not much information on the keyboard itself, but in the video below we catch a glimpse of its wiring as the box is opened.

The value in a terminal using vintage parts lies not only in because you can, but also in something that can’t easily be had with a modern microcontroller. These parts come from a time when a computer system had to be assembled as a series of peripherals round the microprocessor because it had few onboard, leading to a far more in-depth understanding of a computer system. It’s not that a 6809 is a sensible choice in 2020, more that it’s an interesting one.

By comparison, here’s a terminal using technology from today.

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Inside CHIP-8

December 7, 2020 by 4 Comments

Certain old computers — most frequently those using the RCA 1802 — were fond of using an early form of byte-code interpreter for programs, especially games. The interpreter, CHIP-8, was very simple to create but offered high-level features that were tedious to recreate in the native assembly language. Because there are a fair number of simple games written in CHIP-8, there are of course, emulators for it, and [River Gillis] decided to look inside the CHIP-8 byte code interpreter.

Part of the power of CHIP-8 was it only had 35 virtual instructions. That was important when you were trying to shoehorn a game and the interpreter into a very small memory. Remember, in those days 1K of memory wasn’t an unusual number, although the prototypical CHIP-8 host would have 4K.

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Sinclair QL Repairs And Restoration

December 7, 2020 by 9 Comments

[Noel] was in possession of two non-working Sinclair QLs and made a series of videos about his attempts to repair and restore them. If you don’t remember the QL, it was a computer by the famous Clive Sinclair and while it was ahead of its time in some ways, it didn’t become as ubiquitous as some of its siblings or the IBM PC. It did, however, develop an almost cult-like following. You can see the trilogy of videos, below.

The machine was sophisticated for its day–after all, the QL was for quantum leap. Based on a Motorola 68008 processor running at 7.5 MHz, the QL included 128 KB of RAM and could handle up to 896 KB, a respectable amount for 1984. It even had a proprietary network interface. However, it was especially well known for having a pair of microtape drives. These were nicer than cassette tapes but perhaps not as handy as floppy disks. They were, however, cheaper to put into a computer. While there was an official operating system, it wasn’t long before most QL users switched to Minerva, a better OS.

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Giving Micro Channel Bus Computers A Sound Blaster Bark

December 1, 2020 by 15 Comments

Not many people today probably remember what ‘Micro Channel Architecture’ was about, though its acronym ‘MCA’ might ring a bell. Created by IBM to replace ISA (Industry Standard Architecture) and presumably claw back some of that sweet, sweet licensing money, it didn’t quite pan out as IBM hoped. As history shows us, PCI ended up replacing MCA in all of IBM’s systems. The IBM PS/2 systems that used MCA didn’t miss out on classic 1990s cards, such as the original Sound Blaster, but today MCA versions of the Sound Blaster are admittedly rather… rare, not to mention expensive.

But, no longer: decades after the last PS/2 users have moved on, [Tube Time] proudly presents the Snark Barker MCA. It’s a fully Sound Blaster compatible sound card. It supports AdLib synthesis, digital sound playback and recording, as well as a joystick input and MIDI. Based around a Xilinx XC9572XL CPLD and featuring what looks like a full-length MCA card, it would have made an original Sound Blaster card proud.

The GitHub repository not only contains the schematics, BOM and Verilog-based HDL for the CPLD, but also extensive documentation on the assembly and programming. As a bonus, there’s a troubleshooting section which covers some of the joys that came with the sloppy implementations of MCA across systems. Definitely worth a read.

If anyone decides to build this project and use it in their IBM PS/2 system, we would love to hear about it.

Of course, if all you need is a garden variety PCI Sound Blaster clone, the original Snark Barker is the way to go.

(Thanks, Darry)

Urban Explorers Reveal A Treasure Trove Of Soviet Computing Power

November 30, 2020 by 45 Comments

It’s probably a dream most of us share, to stumble upon a dusty hall full of fascinating abandoned tech frozen in time as though its operators walked away one day and simply never returned. It’s something documented by some Russian urban explorers who found an unremarkable office building with one of its floors frozen sometime around the transition from Soviet Union to Russian Federation. In it they found their abandoned tech, in the form of a cross-section of Soviet-era computers from the 1970s onwards.

As you might expect, in a manner it mirrors the development of civilian computing on the capitalist side of the Iron Curtain over a similar period, starting with minicomputers the size of several large refrigerators and ending with desktop microcomputers. The minis seem to all be Soviet clones of contemporary DEC machines. with some parts of them even looking vaguely familiar. The oldest is a Saratov-2, a PDP/8 clone which we’re told is rare enough for no examples to have been believed to have survived until this discovery. We then see a succession of PDP/11 clones each of which becomes ever smaller with advancements in semiconductor integration, starting with the fridge-sized units and eventually ending up with desktop versions that resemble 1980s PCs.

While mass-market Western desktop machines followed the path of adopting newer architectures such as the Z80 or the 8086 the Soviets instead took their minicomputer technology to that level. It would be interesting to speculate how these machines might further have developed over the 1990s had history been different. Meanwhile we all have a tangible legacy of Soviet PDP/11 microcomputers in the form of Tetris, which was first written on an Elektronika 60.

We know that among our readers there is likely to be a few who encountered similar machines in their heyday, and we hope they’ll share their recollections in the comments. Meanwhile we hope that somehow this collection can be preserved one day. If your thirst for dusty mincomputers knows no bounds, read about the collectors who bought an IBM machine on eBay and got more than they bargained for.

Via Hacker News.

DVK-1 desktop computer, «Переславская неделя» / В. С. Спиридонов  CC-BY-SA 3.0.