retrocomputing

364 Articles

FPGA Brings UNIX V1 To The DEC J-11

August 30, 2025 by 12 Comments

If you’ve never used a PDP-11 before it’s probably because you simply weren’t around in the 70s and 80s. Although they started as expensive machines only in research labs and industry, they eventually became much more accessible. They’re a bit of a landmark in computing history, too, being largely responsible for the development of things like UNIX and the C programming language. [ryomuk] is using an FPGA in combination with an original DEC J-11 to bring us a new take on this machine. (Google Translate from Japanese)

The FPGA used in this build is a Tang Nano 20k, notable for its relatively low cost. The FPGA emulates the memory system and UART of a PDP-11 system down to the instruction set, while the original, unmodified DEC chip is left to its own devices. After some initial testing [ryomuk] built a PC11 paper tape emulator to ensure the system was working which runs a version of BASIC from the era. The next thing up was to emulate some disk drives and co-processors so that the machine can run the first version of UNIX. 

[ryomuk] also developed a PCB for the DEC microprocessor and the FPGA to sit on together, and it includes all of the jumpers and wiring needed to allow the computer to run UNIX, as well as handling other miscellaneous tasks like power. It’s an interesting build that gets to the heart of the early days of computer science. PDP-11 computers did eventually get smaller and more accessible, and if you want to build a modern version this build fits a complete system into an ATX case.

Thanks to [RetepV] for the tip!

VIC-20 Gets ISA Slot, Networking

August 26, 2025 by 22 Comments

There are few computing collapses more spectacular than the downfall of Commodore, but its rise as a home computer powerhouse in the early 80s was equally impressive. Driven initially by the VIC-20, this was the first home computer model to sell over a million units thanks to its low cost and accessibility for people outside of niche markets and hobbyist communities.

The VIC-20 would quickly be eclipsed by the much more famous Commodore 64, but for those still using these older machines there are a few tweaks to give it some extra functionality it was never originally designed for like this build which gives it an ISA bus.

To begin adapting the VIC-20 to the ISA standard, [Lee] built a fixed interrupt line handled with a simple transistor circuit. From there he started mapping memory and timing signals. The first attempt to find a portion of memory to use failed as it wasn’t as unused as he had thought, but eventually he settled on using the I/O area instead although still had to solve some problems with quirky ISA timing. There’s also a programmable logic chip which was needed to generate three additional signals for proper communication.

After solving some other issues around interrupts [Lee] was finally able to get the ISA bus working, specifically so he could add a 3Com networking card and get his VIC-20 on his LAN. Although the ISA bus has since gone out of fashion on modern computers, if you still have a computer with one (or build one onto your VIC-20), it is a surprisingly versatile expansion port.

Thanks to [Stephen] for the tip!

Pong Cloned By Neural Network

August 24, 2025 by 9 Comments

Although not the first video game ever produced, Pong was the first to achieve commercial success and has had a tremendous influence on our culture as a whole. In Pong’s time, its popularity ushered in the arcade era that would last for more than two decades. Today, it retains a similar popularity partially for approachability: gameplay is relatively simple, has hardwired logic, and provides insights about the state of computer science at the time. For these reasons, [Nick Bild] has decided to recreate this arcade classic, but not in a traditional way. He’s trained a neural network to become the game instead.

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Dealing With The 1970s EPROM Chaos In 2025

August 23, 2025 by 15 Comments

It could be argued that erasable programmable ROMs (EPROMs) with their quaint UV-transparent windows are firmly obsolete today in an era of various flavors of EEPROMs. Yet many of these EPROMs are still around, and people want to program them. Unfortunately, the earliest EPROMs were made during a time when JEDEC standardization hadn’t taken root yet, leading to unique pinouts, programming voltages, and programming sequences, as [Anders Nielsen] explains in a recent video.

[Anders]’s Relatively Universal-ROM-Programmer project recently gained the ability to program even the oldest types of EPROMs, something which required modifying the hardware design to accommodate EPROMs like Ti’s TMS2716 and the similar-but-completely-different TMS2516. Although not the hardest thing to support – requiring just a diode and resistor added to the BOM along with a firmware update – it’s just one of those pre-standardization traps.

As [Anders] put it, it’s sometimes good to be unencumbered by the burden of future knowledge. Who would have willingly subjected themselves to the chaos of incompatible pinouts, voltages, etc., if they had known beforehand that in a few years EEPROMs and JEDEC standardization would make life so much easier? Maybe that’s why messing with retro hardware like this is fun, as afterwards you can go back to the future.

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Amiga Programming In 2025 With AmiBlitz

August 10, 2025 by 30 Comments

Having owned an Amiga microcomputer is apparently a little bit like having shaken hands with Shoggoth: no one can escape unchanged from the experience. Thirty-two years on, [Neil] at The Retro Collective remains haunted by the memories — specifically, the memory of BlitzBasic 2, an Amiga-specific programming language he never found the time to use. What better time to make a game for the Amiga than the year 2025 of the common era?

[Neil] takes us on a long journey, with more than a little reminiscing along the way. BlitzBasic may not have been the main programming language for the Amiga, but it was by no means the least, with a good pedigree that included the best-selling 1993 game Skidmarks. Obviously BlitzBasic was not a slow, interpreted language as one might think hearing “BASIC”. Not only is it a compiled language, it was fast enough to be billed as the next best thing to C for the Amiga, according to [Neil].

[Neil] wasn’t the only one whose dreams have been haunted by the rugose touch of the Amiga and its scquomose BlitzBasic language– you’ll find a version on GitHub called AmiBlitz3 that is maintained by [Sven] aka [honitas] to this day, complete with an improved IDE. The video includes a history lesson on the open-source AmiBlitz, and enough information to get you started.

For the vibe-coders amongst you, [Neil] has an excellent tip that you can use LLMs like ChatGPT to help you learn niche languages like this not by asking for code (which isn’t likely to give you anything useful, unless you’ve given it special training) but by requesting techniques and psudocode you can then implement to make your game. The LLM also proved a useful assistent for [Neil]’s excel-based pixel art workflow.

If you’re wondering why bother, well, why not? As [Neil] says, writing Amiga games is his version of a crossword puzzle. It may also be the only way to keep the dreams at bay. Others have taken to writing new operating systems  or reproducing PCBs to keep vintage Amiga hardware alive. If some gather under the light of the full moon to chant “Ia! Ia! Commodore f’thagan”– well, perhaps we can thank them for Commodore for rising from the sunless depths of bankruptcy once again.

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Soldered RAM Upgrades Finally Available For Mac-PPC

July 30, 2025 by 8 Comments

In the retrocomputing world, [DosDude1] is a name spoken with more than a little respect. He’s back again with a long-awaited hack for PowerPC Macintosh: soldered RAM upgrades!

[DosDude1] is no stranger to soldering his way to more storage– upgrading the SSD on an M4 Mac Mini, or doubling  the VRAM on an old GPU. For a PPC Mac, though, it is not enough just to solder more RAM onto the board; if that’s all it was, we’d have been doing it 20 years ago. Once the RAM is in place, you have to have some way to make sure the computer knows the RAM is in place. For a WinTel machine, getting that information to the BIOS can be as easy as plugging in the right resistors. Continue reading “Soldered RAM Upgrades Finally Available For Mac-PPC” →

Commodore 64 On New FPGA

July 28, 2025 by 19 Comments

When it comes to getting retro hardware running again, there are many approaches. On one hand, the easiest path could be to emulate the hardware on something modern, using nothing but software to bring it back to life. On the other, many prefer to restore the original hardware itself and make sure everything is exactly as it was when it was new. A middle way exists, though, thanks to the widespread adoption of FPGAs which allow for programmable hardware emulation and [Jo] has come up with a new implementation of the Commodore 64 by taking this path.

The project is called the VIC64-T9K and is meant as a proof-of-concept that can run the Commodore 64’s VIC-II video chip alongside a 6502 CPU on the inexpensive Tang Nano 9k FPGA. Taking inspiration from the C64_MiSTer project, another FPGA implementation of the C64 based on the DE10-Nano FPGA, it doesn’t implement everything an original Commodore system would have had, but it does provide most of the core hardware needed to run a system. The project supports HDMI video with a custom kernel, and [Jo] has used it to get a few demos running including sprite animations.

Built with a mix of Verilog and VHDL, it was designed as a learning tool for [Jo] to experiment with the retro hardware, and also brings a more affordable FPGA board to the table for Commodore enthusiasts. If you’re in the market for something with more of the original look and feel of the Commodore 64, though, this project uses the original case and keyboard while still using an FPGA recreation for the core of the computer.