PC-XT

7 Articles

There’s Always Room For Another Cycle Accurate PC Emulator

July 3, 2023 by 16 Comments

While many Hackaday readers will have their own pieces of classic hardware lovingly preserved, it still remains that most of us get our fix of retro goodness through emulation. And while there are emulators aplenty for almost every platform imaginable, the world of emulation is never complete. Thus we’re happy to encounter a new player in the form of MartyPC, a cycle-accurate 8088 PC emulator written in Rust.

It’s a project that started only in April 2022, but alongside such in-depth processor support it has the full range of PC and XT peripherals including CGA and VGA cards to the extent that it will run even the most hardware-demanding demos. Below the break you can see it running the fiendishly hardware-specific PC demo Area 5150 — thought to be the first time an emulator has managed this task.

If there’s a snag it’s that the releases are so far Windows-only, though it’s claimed that it should also compile on other major platforms. There’s also a WebAssembly version, though sadly the link to it doesn’t work. We look forward to this emulator maturing, because we’re sure it will become a PC standby. After all, not everyone managed to snag one of the recent batch of new hardware.

Continue reading “There’s Always Room For Another Cycle Accurate PC Emulator” →

Connecting A Keyboard To A Vintage PC-XT, The Hard Way

February 7, 2023 by 16 Comments

We’re not sure if there’s any single characteristic that qualifies someone as a hacker. After all, we’re a pretty eclectic bunch, with skills that range all over the map, and what one person feels is trivial, others would look upon as black magic. But there’s one thing we’re sure of: if you find yourself reading the original POST code for the PC-XT motherboard just to get a keyboard working, you’re pretty much our kind of people.

That was the position [Anders Nielsen] found himself in as work progresses on his “PC-XT from Scratch” project, which seeks to build a working mid-80s vintage IBM Model 5160 using as many period-correct parts as possible. The first installment of the series featured the delicate process of bringing the motherboard up, lest the magic smoke was released. After seeing some life out of the old board, [Anders] needed a little IO, specifically video and keyboard. The video side of the equation was relatively trivial, with an early-90s VGA card from eBay — not exactly period correct, but good enough to get something to display. Continue reading “Connecting A Keyboard To A Vintage PC-XT, The Hard Way” →

Bringing Up An Old Motherboard Is A Delicate Process

November 12, 2022 by 12 Comments

If you were around for the early days of the personal computer revolution, you’ll no doubt recall the excitement every time IBM announced a new version of its beige boxes. For a lot of us, the excitement was purely vicarious, for despite the “personal” moniker, mere mortals could rarely afford a branded IBM machine. But it was still cool to keep track of the latest releases, and dream of the days when cheap clones would make it possible to play.

[Anders Nielsen]’s recent find of an original IBM Model 5160 motherboard sort of echoes that long-ago excitement, but in a different way. This board, from a PC XT built in 1984, was in unknown condition upon arrival, so [Anders] set about a careful process to try to bring the board back to life. A quick visual inspection leaves one with a sense of both how much things have changed, and how much they’ve stayed the same. Aside from the big 40-pin DIP 8088 CPU and the BIOS ROMs, the board is almost completely populated with discrete logic chips, but at the same time, the basic footprint of a motherboard has changed very little.

The bring-up process in the video below includes checks of all the power rails for shorts, which ended up being a good call — drat those tantalums. After fixing that issue, [Anders] had a bit of trouble getting the board to POST, and eventually resorted to dumping the BIOS ROMs and inspecting the contents. One of the chips had picked up a case of the scramblies at some point, which was easy enough to fix thanks to images of the 5160 ROMs available online. We thought the trick of using a 64k ROM and just writing the BIOS image twice was pretty clever.

In the end, the board came up, although without video or keyboard — that’s for another day. Can’t find your own PC XT motherboard to play with? Then maybe you can just build one.

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Building Your Own 8088 XT Motherboard

May 21, 2022 by 47 Comments

There was a time when an XT-class motherboard — like the old IBM PC with an 8088 CPU — was a high-tech accomplishment. Now, something like that is easily within reach of the average hobby lab. [Homebrew8088] did it, and it looks surprisingly simple, especially compared to what passes for a motherboard these days.

The board will take an 8088 or one of the NEC chips and by default sports 512 K of RAM, a few ISA slots, a PC speaker, a USB hard drive, and a PS/2 keyboard connector. The board will fit in an ATX case. Not bad. You can see a video of the board below.

In fact, the channel has a lot of related videos and the main site has many interesting topics, like driving an 8088 or 8086 from a Raspberry Pi. The GitHub site has design files for KiCad along with a lot of other information. Some of this will be interesting even if you are just trying to repair an old motherboard or would like to design a new ISA card.

If you want to know why the PC used an 8088 instead of an 8086, we just covered that. What are you going to do with an old XT computer? How about IRC?

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Making Vintage Computing Easy, The Hard Way

May 4, 2018 by 35 Comments

If you want to not take for granted how easy and seamless computers have become, take up vintage computing as a hobby. If you venture down the retro path, you’ll quickly question how anyone ever got any useful work done with computers, and the farther back you go in computer history, the more difficult everything seems to become.

Case in point: how do you easily transfer files between a home-brew PC/XT and your modern desktop? Back in the day we did it with null modem cables or by sneaker-netting stacks of floppies, but [Scott M. Baker] found another way — putting a Raspberry Pi on the ISA bus as a virtual floppy drive. The heart of the ISA card is an IDT7130, a 1-kb RAM chip that allows simultaneous asynchronous access over dual ports. One port talks to the ISA bus and the other talks to the GPIO of the Pi, after level-shifting to make everything voltage compatible, of course. [Scott] wrote a driver for the card, plugged a Pi Zero W into the header pins, and threw a Python server together that makes local images available to the shared memory on the card. The upshot of this is that the retro machine thinks it has a floppy in it, but it’s actually a server. The video below has tons of detail and shows the card in action. Pretty slick.

[Scott]’s projects are always fun to check out, and he really seems to have the retro life dialed in. Whether it’s old jukebox hacks or a Unix-ish OS for Z80s, there’s plenty to learn. Although we’d like to see more about that PC/XT in the video; are those Nixies we spy along the front panel?

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x86 emulation running DOS on ESP8266

PC-XT Emulator On ESP8266

February 26, 2018 by 58 Comments

Do you remember the simpler times when you had a DOS command line, a handful of commands, and you talked to the hardware through a few BIOS and DOS interrupts? Okay, maybe it was a little limited, but nostalgia doesn’t care. Now [mcuhacker] is working on bringing some of those memories back by getting a PC-XT emulator running on an ESP8266.

For the x86 CPU emulator, he ported Fake86 which is written in C, and created an Arduino IDE environment for it. The MS-DOS 3.3 bootdisk image is stored in flash and is accessed as the A: drive. There’s no keyboard yet but he has 640×200 CGA working with 80×25 characters on a 3.5″ TFT display with the help of a low pass filter circuit. In the video below he shows it booting to the point where it asks for the date.

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Hackaday Prize Entry: A PC-XT Clone Powered By AVR

May 21, 2017 by 19 Comments

There is a high probability that the device on which you are reading this comes somehow loosely under the broad definition of a PC. The familiar x86 architecture with peripheral standards has trounced all its competitors over the years, to the extent that it is only in the mobile and tablet space of personal computing that it has not become dominant.

The modern PC with its multi-core processor and 64-bit instruction set is a world away from its 16-bit ancestor from the early 1980s. Those early PCs were computers in the manner of the day, in which there were relatively few peripherals, and the microprocessor bus was exposed almost directly rather than through the abstractions and gatekeepers we’d expect to see today. The 8088 processor with an 8-bit external bus though is the primordial PC processor, and within reason you will find software written for DOS on those earliest IBM machines will often still run on your multiprocessor behemoth over a DOS-like layer on your present-day operating system. This 35-year-plus chain of mostly unbroken compatibility is both a remarkable feat of engineering and a millstone round the necks of modern PC hardware and OS developers.

Those early PCs have captured the attention of [esot.eric], who has come up with the interesting project of interfacing an AVR microcontroller to the 8088 system bus of one of those early PCs. Thus all those PC peripherals could be made to run under the control of something a little more up-to-date. When you consider that the 8088 ran at a modest 300KIPS and that the AVR is capable of running at a by comparison blisteringly fast 22MIPS, the idea was that it should be able to emulate an 8088 at the same speed as an original, if not faster. His progress makes for a long and fascinating read, so far he has accessed the PC’s 640KB of RAM reliably, talked to an ISA-bus parallel port, and made a CGA card produce colours and characters. Interestingly the AVR has the potential for speed enhancements not possible with an 8088, for example it can use its own internal UART with many fewer instructions than it would use to access the PC UART, and its internal Flash memory can contain the PC BIOS and read it a huge amount faster than a real BIOS ROM could be on real PC hardware.

In case you were wondering what use an 8088 PC could be put to, take a look at this impressive demo. Don’t have one yourself? Build one.

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