Retrocomputing

1192 Articles

Remembering Seymour Cray

July 16, 2024 by 28 Comments

If you think of supercomputers, it is hard not to think of Seymour Cray. He built giant computers at Control Data Corporation and went on to build the famous Cray supercomputers. While those computers aren’t especially amazing today, for their time, they were modern marvels. [Asianometry] has a great history of Cray, starting with his work at ERA, which would, of course, eventually produce the computer known as the Univac 1103.

ERA was bought up by Remington Rand, which eventually became Sperry Rand. Due to conflict, some of the ERA staff left to form Control Data Corporation, and Cray went with them. The new company decided to focus on computers to do simulations for things like nuclear test simulations.

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Wrap Your Keyboard With A Vacuum Former

July 14, 2024 by 4 Comments

Coloured keycaps are a common customisation when it comes to making your input device special. If you are working with modern tech it’s easy, there are plenty of vendors who can sell you keycaps for any purpose. With retro tech it’s never so simple, if a keycap hasn’t been made for decades you’re out of luck. This doesn’t faze [Drygol] though, who has solved the coloured retro keycap in a unique and non-destructive way. Wrap them in vinyl film using a vacuum former.

Vacuum formers are an often-underrated tool in the hardware arsenal, but as this project shows, they can produce startlingly good results. Original keycaps are placed on a 3D-printed scaffold before the vinyl is formed over them, then they are carefully cut out and a triangular edge on both sides is folded underneath, The result is an Amiga with a striking orange keyboard, and for us the best bit is that the original key is safely preserved under the vinyl.

[Drygol]’s exceptional work in the retrocomputing sphere has delighted us many times on these pages. There are too many examples to link here, but one we particularly liked was this nearly-all-new Amiga 2000.

Making SD Cards More Nostalgic With More Cartridge-ness

July 12, 2024 by 11 Comments

As practical SD cards are, they lack much of what made floppy disks and cartridges so awesome: room for art and a list of contents, as well as the ability to not be lost in shaggy carpet or down a pet’s gullet. In a fit of righteous nostalgia, [Abe] decided that he’d turn SD cards into cartridges in the best way possible, and amazingly managed to not only finish the project after two years, but also make it look snazzy enough to have come straight out of the 1980s. The resulting cartridges come both with fixed (256 MB) and removable micro SD card storage, which are mounted on a PCB that passively connects to pogo pins in the custom, 3D printed reader.

Front of an SD-card-turned-cartridge with adn without decal. (Credit: Abe's Projects, YouTube)
Front of an SD-card-turned-cartridge with and without decal. (Credit: Abe’s Projects, YouTube)

The inspiration for this project kicked in while [Abe] was working on a floppy drive conversion project called the Floppy8, which crammed an MCU into an external floppy drive along with a rough version of these SD card-based cartridges that used the physical card’s edge connector to connect with a micro SD slot inside the converted floppy drive. The problem with this setup was that alignment was terrible, and micro SD cards would break, along with a range of other quality of life issues.

Next, the SD card was put into a slot on the carrier PCB that featured its own edge connector. This improved matters, but the overly complicated (moving) read head in the reader turned out to be very unreliable, in addition to FDM printed parts having general tolerance and durability issues. Eventually a simplified design which takes these limitations in mind was created that so far seems to work just fine.

Although SD cards in cartridges are not a new idea, using them purely as a data carrier is far less common. One could argue about the practicality of turning a fingernail-sized micro SD card into something much larger, but in terms of aesthetics and handleability it definitely gets an A+.

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Build Your Own 16 MB 30-Pin SIMMs For Vintage PCs

July 9, 2024 by 28 Comments

Today’s memory sticks have hundreds of pins and many gigabytes of RAM on board. Decades ago, though, the humble 30-pin SIMM was the state of the art where memory was concerned. If you’ve got vintage gear, you can try and hunt down old RAM, or you can copy [Bits und Bolts] and make your own.

Previously, [Bits und Bolts] built a 4 MB SIMM, but he’s now ramped up to building 16 MB RAM sticks — the largest size supported by the 30-pin standard. That’s a ton compared to most 30-pin sticks from the 1980s, which topped out at a feeble 1 MB.

We get to see four of his 16 MB sticks installed in a 386 motherboard, set up to operate in the appropriate Fast Page Mode. He was able to get the system operating with 64 MB of RAM, an amount still considered acceptable in the early Pentium 3 era. Hilariously, memtest took a full ten hours to complete a single pass with this configuration. [Bits and Bolts] also tried to push the motherboard further, but wasn’t able to get it to POST with over 64 MB of RAM.

As [Bits und Bolts] demonstrates, if you can read a schematic and design a PCB, it’s not that hard to design RAM sticks for many vintage computers. We’ve seen some other RAM hacks in this vein before, too.

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[Usagi Electric’s] Bendix G15 Gets DC Power

July 8, 2024 by 2 Comments

[Usagi Electric] is breathtakingly close to having his Bendix G15 vacuum tube computer up and running. This week he is joined by a new friend, [Lloyd] who is restoring a G15 as well. [Lloyd] used to repair the Bendix Computers back in the 1970s, so he’s privy to lots of practical knowledge you can’t find in the manuals.

The goal this week was to apply DC power to the G15.  The AC power spins the fans and makes the tubes start glowing. But DC makes the magic happen.  That’s when the boot sequencers start running, sending data to the drum, testing various parts of the machine, and finally, loading software from the paper tape reader.

Since this was a computer from the 1950’s, powering up DC might work, or could let the magic smoke out.  The only way to find out was to push the big green “Reset” button.

The first attempt was stymied by a blown fuse. The second attempt resulted in real live blinkenlights. The data and status lights on the Bendix lit up for the first time in decades. The only thing missing was the sound of the tape drive.  A bit of digging proved that the problem wasn’t in the computer, but in the typewriter user console. The typewriter is supposed to connect the SA line to the -20 volt DC rail. That wasn’t happening though. Since that expected voltage wasn’t present on the SA line at the Bendinx, the boot process halted.

Unfortunately, the typewriter has “somebody’s been here before” syndrome – in addition to age, there are a number of odd modifications.  It’s going to take [Usagi] a bit of time to dig into it and figure out what’s wrong.

The good news is that the computer is using its massive spinning drum drive. [Usagi] was able to verify this with the test panel inside the machine. One button will write a pulse to the drum, and another will erase it. Manipulating these buttons, [Usagi] could see the results on an oscilloscope.  This may sound simple – but just getting to this point means an incredibly complex chain of tube, relay, and mechanical logic has to work.  Bravo [Dave] and [Lloyd]!

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Custom Microcode Compiler, Made In Google Sheets

July 7, 2024 by 12 Comments

When homebrewing a CPU, one has to deal with microcode. Microcode is the low-level nuts and bolts of how, precisely, a CPU executes instructions (like opcodes) and performs functions such as updating the cycle counter or handling interrupt requests. To make this task easier, [Bob Alexander] created a microcode compiler built in Google Sheets to help with his own homebrew work, but it’s flexible and configurable enough to be useful to others, as well.

A CPU’s microcode usually lives in read-only memory, and writing the microcode is only one step in the journey. [Bob]’s tool compiles his microcode into files that can be burned into memory (multiple EEPROM chips, in [Bob]’s case) or used as a Verilog program in the case of implementing the CPU in an FPGA. It’s configurable enough to be adapted for other homebrew CPU projects, though one would of course have to re-write the microcode portion.

A read-only version of the spreadsheet makes for some fun browsing, and if it piques your interest enough to get a copy of your own complete with the compiler script, you can do that here. It uses Google Sheets, and writes the output files into one’s Google Drive.

This kind of low-level project really highlights the finer points of just how the hard work of digital computing gets done. A good example is the Gigatron which implemented a RISC CPU using only microcode, memory, and logic gates in the late 70s. We’ve even seen custom microcode used to aid complex debugging.