A Love Letter To The Sphere Computer

March 11, 2023 by Al Williams 21 Comments

[Ben Z] loves the Sphere computer, a very early entry in the personal computer boom of the mid 1970s. The 6800 CPU was unique in its day that it was a full system — at least in theory. If you could afford the whole system, you got a nice case with a keyboard and a memory-mapped display board. You can see a great video tour of the system below the break.

The Sphere suffered from a few problems, none of which were easily foreseeable by its designer. First, the 6800 didn’t get the traction that the 8080-derived CPUs did. Second, the S-100 bus would prove to be popular but that nearly always meant an 8080-type processor in practice. Third, while an all-in-one system was the right idea, it was pricey at the time, and many people would opt for something less expensive even if it had less capability. People also wanted to leverage hardware they may have already had. It was easier to imagine hooking up a surplus TeleType, for example, to a more conventional computer than to a Sphere that expected its own display hardware and keyboard.

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A Close Look At A Little Known 8-bit Computer

April 8, 2022 by Al Williams 47 Comments

If you read about the history of personal computing, you hear a few familiar names like Microsoft, Apple, and even Commodore. But there were a host of companies that were well known and well regarded back then that are all but forgotten today. Godbout computing, Ohio Scientific, and Southwest Technical Products (SWTP). SWTP is probably best remembered for having a relatively cheap printer and “TV typewriter”, but they also made a 6800-based computer and [Adrian] takes us inside of one.

The 6800 was Motorola’s entry into the microprocessor fray, competing with the Intel 8080. The computer came out scant months after the introduction of the famous Altair 8800. Although the Altair is often credited as being the first hobbyist-grade computer, there were a few earlier ones based on the 8008, but the Altair was the first to be successful.

The SWTP was notable for its day for its blank appearance. Most computers in those days had lots of switches and lights. The SWTP has a blank front with only a power switch and a reset button. A ROM monitor let you use the machine with a terminal. For about the same price as a bare-bones Altair that had no interfaces or memory, you could pick one of these up with most of the extras you would need. The memory was only 2K, but that was 2K more than you got with an Altair at that price point.

The $450 sounds fairly cheap, but in the early 70s, that was a lot of lawns to mow. Of course, while you’d need to add memory to the Altair, you’d have to add some kind of terminal to the SWTP. However, you’d wind up with something more usable but the total bill was probably going to approach $1,000 to get a working system.

Inside the box were some old-fashioned-looking PC boards and connectors that will look familiar to anyone who has been inside 1970s gear. Will it work? We don’t know yet, but we hope it does. [Adrian] promises that will be in the next video.

It is amazing how far we’ve come in less than 50 years. A postage-stamp sized $10 computer now has enough speed and memory to emulate a bunch of these old machines all at once. The SWTP has been on our pages before. A lot of these old machines and companies are all but forgotten, but not by us!

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Retro Computer Trainer Gets A Raspberry Pi Refit

October 12, 2020 by Dan Maloney 11 Comments

We know what you’re thinking: this is yet another one of those “Gut the retro gear for its cool old case and then fill it up with IoT junk” projects. Well, rest assured that extending and enhancing this 1970s computer trainer is very much an exercise in respecting the original design, and while there’s a Pi inside, it doesn’t come close to spoiling the retro goodness.

Like many of a similar vintage as [Scott M. Baker], the Heathkit catalog was perhaps only leafed through marginally less than the annual Radio Shack catalog. One particularly desirable Heathkit item was the ET-3400 microcomputer learning system, which was basically a 6800-based computer surrounded by a breadboarding area for experimentation. [Scott] got a hold of one of these, but without the optional expansion accessory that would allow it to do interesting things such as running BASIC or even supporting a serial port. So [Scott] decided to roll his own expansion board.

The expansion card that [Scott] designed is not strictly a faithful reproduction, at least in terms of the original BOM. He turned to more modern — and more readily available — components, but still managed to provide the serial port, cassette interface, and RAM/ROM expansion of the original unit. The Raspberry Pi is an optional add-on, which just allows him to connect wirelessly if he wants. The card fits into a 3D-printed case that sits below the ET-3400 and maintains the original trainer’s look and feel. The longish video below shows the build and gives a tour of the ET-3400, both before and after the mods.

It looks as though trainers like these and other artifacts from the early days of the PC revolution are getting quite collectible. Makes us wish we hadn’t thrown some things out.

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FPGA 6800 Uses Python Toolbox

December 27, 2019 by Al Williams 7 Comments

Usually, when you think of designing — or recreating — a CPU on an FPGA, you assume you’ll have to use Verilog or VHDL. There are other options, as well, but those are the biggest two players in FPGA configuration. [Robert Baruch] has a multipart series where he uses nMigen — a Python toolbox — to recreate a 6800 CPU like the one used in many vintage video games and pinball machines.

Unlike some tools that try to convert software written in some language to an FPGA configuration, nMigen uses Python as a scripting language to create code in FHDL. This is similar in concept to VHDL or Verilog, but gives up the event-driven paradigm, opting instead to allow designers to explicitly call out synchronous and combinatorial logic.

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