isa bus

8 Articles

Possibly The Newest ISA Card

October 10, 2025 by 13 Comments

Back when the IBM PC was new, laying out an ISA board was a daunting task. You probably didn’t have a very fast ‘scope, if you had one at all. Board layout was almost certainly done on a drafting table with big pieces of tape. It was hard for small companies, much less hobbyists, to make a new card. You could buy a prototype board and wirewrap or otherwise put together something, but that was also not for the faint of heart. But with modern tools, something like that is a very doable project and [profdc9] has, in fact, done it. The card uses an ATMega328P and provides two SD cards for use as mass storage on an old computer.

The design tries to use parts that won’t be hard to get in the future. At least for a while, yet. There’s capacity for expansion, too, as there is an interface for a Wiznet 5500 Ethernet adapter.

Continue reading “Possibly The Newest ISA Card” →

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!

PicoGUS Adds CD-ROM Emulation To ISA Bus

July 19, 2025 by 29 Comments

Everything fails eventually, but moving parts fail fastest of all– and optical drives seemingly more than others, at least in our experience. Even when they work, vintage drives often have trouble with CD-R, and original media isn’t always easy to find. That’s why it’s so wonderful that [polpo]’s RP2040 ISA card, the PicoGUS 2.0, now supports CD-ROM emulation.

We covered PicoGUS when it first appeared as an ISA sound card,  and make no mistake, it can still emulate sound cards for retro-PC beeps and boops. It’s not just the Gravis Ultrasound (GUS) from which the project took its name, but Sound Blaster 2.0, MPU-401 for MIDI, Tandy 3-voice, and CMS/GameBlaster are all soft options. Like most sound cards back in the day, PicoGUS provides game port support as well.

Continue reading “PicoGUS Adds CD-ROM Emulation To ISA Bus” →

PicoGUS: For All Your ISA Sound Card Needs

November 21, 2023 by 23 Comments

Sound cards used to be a big part of gaming machines in the 90s and 2000s but have largely gone extinct in the wake of powerful CPUs doing the sound themselves. Sound cards were expensive back then and, because the good ones weren’t very common, are expensive still for the retro gamer. But if you don’t need the real thing, [polpo] has you covered with his RP2040-based ISA sound card.

The PicoGUS, as he calls it, primarily serves to replace the Gravis UltraSound with modern components at a low cost. It uses the RP2040’s PIO to attach to an ISA bus and the RP2040’s dual-core power to synthesize the audio for its primary target, but also the AdLib (OPL2), CMS/Game Blaster and Tandy 3-Voice. [polpo] sells the PicoGUS on his Tindie store, but since it’s open source, you can of course just make your own.

Although “work-in-progress”, the PicoGUS is very useful to the right person and a perfect demonstration of how the RP2040’s PIO can be used to interface with almost any type of protocol.

Of couse, that’s not the only way to use the PIO, you can also create a CAN bus or even add another USB port.

A 386 motherboard with a custom ISA card plugged in

Emulate Any ISA Card With A Raspberry Pi And An FPGA

November 13, 2022 by 28 Comments

One of the reasons the IBM PC platform became the dominant standard for desktop PCs back in the mid-1980s was its open hardware design, based around what would later be called the ISA bus. Any manufacturer could design plug-in cards or even entire computers that were hardware and software compatible with the IBM PC. Although ISA has been obsolete for most purposes since the late 1990s, some ISA cards such as high-quality sound cards have become so popular among retrocomputing enthusiasts that they now fetch hundreds of dollars on eBay.

So what can you do if your favorite ISA card is not easily available? One option is to head over to [eigenco]’s GitHub page and check out his FrankenPiFPGA project. It contains a design for a simple ISA plug-in card that hooks up to a Cyclone IV FPGA and a Raspberry Pi. The FPGA connects to the ISA bus and implements its bus architecture, while the Pi communicates with the FPGA through its GPIO ports and emulates any card you want in software. [eigenco]’s current repository contains code for several sound cards as well as a hard drive and a serial mouse. The Pi’s multi-core architecture allows it to run several of these tasks at once while still keeping up the reasonably high data rate required by the ISA bus.

In the videos embedded below you can see [eigenco] demonstrating the system on a 386 motherboard that only has a VGA card to hook up a monitor. By emulating a hard drive and sound card on the Pi he is able to run a variety of classic DOS games with full sound effects and music. The sound cards currently supported include AdLib, 8-bit SoundBlaster, Gravis Ultrasound and Roland MT-32, but any card that’s documented well enough could be emulated.

This approach could also come in handy to replace other unobtanium hardware, like rare CD-ROM interfaces. Of course, you could take the concept to its logical extreme and simply implement an entire PC in an FPGA.

Continue reading “Emulate Any ISA Card With A Raspberry Pi And An FPGA” →

Card's author typing on the IBM PC110's keyboard, with the Pico W-based card plugged into the PCMCIA slot on the left. PC110's screen shows successful ping 8.8.8.8.8.

Pi Pico W Does PCMCIA, Gets This IBM PC110 Online

September 25, 2022 by 37 Comments

Bringing modern connectivity to retro computers is an endearing field- with the simplicity of last-century hardware and software being a double-edged sword, often, you bring a powerful and tiny computer of modern age to help its great-grandparent interface with networks of today. [yyzkevin] shows us a PCMCIA WiFi card built using a Pi Pico W, talking PCI ISA. This card brings modern-day WiFi connectivity to his IBM PC110, without requiring a separate router set up for outdated standards that the typical PCMCIA WiFi cards are limited by.

The RP2040 is made to talk PCI ISA using, of course, the PIO engine. A CPLD helps with PCI ISA address decoding, some multiplexing, and level shifting between RP2040’s 3.3V and the PCI 5 V levels. The RP2040 software emulates a NE2000 network card, which means driver support is guaranteed on most OSes of old times, and the software integration seems seamless. The card already works for getting the PC110 online, and [yyzkevin] says he’d like to improve on it – shrink the design so that it resembles a typical PCMCIA WiFi card, tie some useful function into the Pico’s USB port, and perhaps integrate his PCMCIA SoundBlaster project into the whole package while at it.

This is a delightful project in how it achieves its goal, and a pleasant surprise for everyone who’s been observing RP2040’s PIO engine conquer interfaces typically unreachable for run-of-the-mill microcontrollers. We’ve seen Ethernet, CAN and DVI, along many others, and there’s undoubtedly more to come.

We thank [Misel] and [Arti] for sharing this with us!

You Got Something On Your Processor Bus: The Joys Of Hacking ISA And PCI

January 6, 2021 by 32 Comments

Although the ability to expand a home computer with more RAM, storage and other features has been around for as long as home computers exist, it wasn’t until the IBM PC that the concept of a fully open and modular computer system became mainstream. Instead of being limited to a system configuration provided by the manufacturer and a few add-ons that really didn’t integrate well, the concept of expansion cards opened up whole industries as well as a big hobbyist market.

The first IBM PC had five 8-bit expansion slots that were connected directly to the 8088 CPU. With the IBM PC/AT these expansion slots became 16-bit courtesy of the 80286 CPU it was built around. These slots  could be used for anything from graphics cards to networking, expanded memory or custom I/O. Though there was no distinct original name for this card edge interface, around the PC/AT era it got referred to as PC bus, as well as AT bus. The name Industry Standard Architecture (ISA) bus is a retronym created by PC clone makers.

With such openness came the ability to relatively easy and cheaply make your own cards for the ISA bus, and the subsequent and equally open PCI bus. To this day this openness allows for a vibrant ecosystem, whether one wishes to build a custom ISA or PCI soundcard, or add USB support to a 1981 IBM PC system.

But what does it take to get started with ISA or PCI expansion cards today? Continue reading “You Got Something On Your Processor Bus: The Joys Of Hacking ISA And PCI” →