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Comment by qwerty456127 | Hacker News Reader

What I (and, probably, a lot of people) would actually like to have is a 486 emulator (with at least 8 MB RAM) with a working ISA bus I could connect old extension cards to. That would be a way more practical (in fact insanely cool) although a ghost of a genuine antique like 640K XT still surely is a fun thing to touch. That could even have commercial applications - I believe there are many 486/ISA-based solutions still running in production in the wild.

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There's ISA to USB devices for under $40 so you can hook the hardware up to a modern machine

Then I'm sure you can use one of the many emulator solutions on the market to bridge the rest and if none are suitable it can't be that hard, the data is making it to the machine...

I'll happily make it happen if you need to hack something like qemu, sounds like fun.

I think a lot of these ISA cards are for industrial control in realtime systems, so the added latency of USB is not going to work.

Are you sure? We aren't in the world of USB 1.1 latency any more. Things have improved vastly since then.

There's still latency getting data DMAed through buffers from Host to slave no matter how fast the link is. It's also non-deterministic.

I found two people who measured latencies, one a PCIe parallel port and the other USB 3.0:

https://stackoverflow.com/questions/41987430/what-is-the-low...

https://stackoverflow.com/questions/13831008/what-is-the-min...

PCIe parallel port: 4-8us

USB 3.0: 30us

I believe a regular PCI or even ISA parallel port can be below 1us. Those are "real" buses, unlike USB and PCIe which are more similar to packet-switched networks.

I don’t know about ISA, but pci (not e) can easily be under 1us. It would be an odd design to have even that much latency.

As measured on the bus.

Theoretical one-way latency on PCIe 3.0 ×1 for a 256-byte packet is < 0.5µs. A single register write should be < 0.1µs.

Not only are they used in production, new boards are still being made and sold today. Search for PC104, which specifies a common form factor and interfaces.

There are also adapters for connecting PC104 to ISA.

Re: PC/104: There’s actually a few different variations of it. The original one used an ISA bus, yes, but as new buses were developed, new “versions” of PC/104 were released:

* PC/104: ISA

* PC/104 Plus: ISA/PCI

* PCI/104: PCI

* PCI/104 Express: PCI/PCIe

* PCIe/104: PCIe

You can easily get ARM MCUs with parallel bus interfaces, stick a CPLD on and you can make ISA out of that. The trickiest part is likely ISA DMA emulation.

e.g. STM32H750 (< $10, Cortex-M7, 480 MHz, 1MB RAM) should easily give you room for emulating a 486.

> 486/ISA-based solutions still running in production in the wild

I shudder to confirm that you are correct.

And the day one of mine truly breaks down is probably going to be the day I go looking for a new job. >D

You can buy native x86 w ISA boards still.

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