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Unfortunately that's not a truly "modern" motherboard as it's from around 2011, and newer ones no longer support LPC DMA. If my research is correct, the last Intel chipset to support LPC DMA should be the X99 from 2014, but even before that, e.g. Atom x2000 series (2012), LPC DMA was already missing.

I've not had the time to prove this out, but I believe it should still be possible to have full ISA support, including DMA, via a PCI/PCIe bridge that also needs to contain a pair of 8237-compatible DMA controllers and act as a bus master to buffer and translate ISA DMA requests to PCI/PCIe requests. It'll probably need an option ROM to configure the interrupt controllers and related signal paths in an ISA-compatible fashion. It might make a good exercise to implement one using an FPGA.

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The X299 (2017) PCH certainly still has the proper DMAC for LPC[1]. The first series you see lacking a DMAC core (or, at least one compatible with LPC/ISA DMA) is the consumer 200 series of PCHs[2]. And it was fully gone by the 300 series[3]. It would seem that something in the switchover to the new streamed Intel HDA DMA architecture or going from DMI2.0->DMI3.0 left the functionality to the wayside.

1 - [PDF] https://cdrdv2-public.intel.com/335899/335899-005.pdf

2 - [PDF] https://www.intel.com/content/dam/www/public/us/en/documents...

2 - [PDF] - https://www.intel.com/content/dam/www/public/us/en/documents...

The X299 (2017) PCH certainly still has the proper DMAC for LPC[1].

That's a link to a CPU datasheet. The X299 datasheet is your second link, which you can see mentions "LPC 24 MHz, No DMA" on page 19.

(I hope I'm not talking to a GPT here.)

What about on the AMD side. Is there still any compatibility there?

I wouldn't be surprised if you could bit bang ISA these days. ISA ran at 8MB/s, and (e.g.) a Raspberry Pi runs at 1.5GHz. That's nearly 200 cycles per ISA clock. All you need is a couple of i/o pins.

A friend of mine is building a Raspberry Pi ISA board so I’ll have to ping him on how it’s going.

An RPi is not so much different from a PC in that the CPU core clock is going to be the fastest and everything else will be slower. You're not going to get 1.5GHz out of a GPIO.

https://raspberrypi.stackexchange.com/questions/100011/how-f...

You don’t need to. Your cap is 8MB/sec. For audio you don’t even need that. 48khz 16bit stereo is only 192k/sec.

I've seen some astounding projects using the Raspberry Pi Pico "PIO" to create n64 Flash carts and now HDMI adapters. I don't have the slightest knowledge of how this stuff works but I imagine it is some sort of bit banging like process. Do you think it would be possible to simulate something like a soundcard using Raspberry Pi Pico? These devices seem like a great and really cost effective way to design around expensive FPGA based designs.

picogus: https://www.vogons.org/viewtopic.php?f=62&t=88440

https://github.com/polpo/picogus/

Truly Amazing! Thank you for the link!

I'm the creator of PicoGUS... PIO is kind of like hardware assisted bit banging. You program a very simple, extremely fast computer (aka the PIO peripheral on the RP2040) to do the bit banging for you. :)

I would. Doing bitbanging reliably is easy only if you have single process running.

But it might work if ISA card doesn't rely on clock being constant all that much, then any jitter in CPU transfer shouldn't matter too much.

ISA is very forgiving timing wise. As long as you have the data on the pins when IOR or do your read by the time IOW is deasserted by the chipset you’re fine. And you can always deassert IOCHRDY and get all the time in the world to respond (within reason).

Bit-banging one I'd be surprised about mostly for signal integrity at that line-speed reasons.

However even a home silk-screened PCB could probably handle that and a USB control connection. Without deep knowledge hard part's likely the software, getting the connected item to work; probably as a virtual hardware device in a KVM or other emulated guest OS with the illusion it's on old hardware.

It may be possible if you programmed the pi bare metal, I can't imagine a non rt os working.

https://github.com/osnr/rpi-bitbang-ethernet

Might be possible, someone bitbanged (sending) ethernet frames.

This example makes me convinved that if you added a clock and some latches to a raspberry pi, it definitely should be able to do ISA bus.

Maybe even without any hardware, who knows. But it needs to level shift from 3V to 5V anyway.

I had terrible luck getting 48k audio out of a bit-banged I2C ADC over Raspberry Pi. Being in userland was the most noticeable problem; once I switched to a kernel driver I was barely able to get the right sample rate.

I had some very successful experiments with bit banging ISA on a Raspberry Pi 3 and 4 a while ago: https://github.com/polpo/pigus I quickly moved over to a Raspberry Pi Pico because it's much better suited to such things. You need more than a couple I/O pins, though... to do real ISA (i.e., not LPC) right, you need more GPIOs than what the Pi gives you. But muxing the data/address lines is enough to give you back what you need.

It's still more modern than ISA

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