I actually considered making that ISA board. I have the ISA prototype boards and the DACs. The DACs are 'DAC8412F' from analog devices
www.analog.com, they are quad 12 bit dacs with bi-polar +/-10 volt outputs.
The reason I didn't continue was because I needed all the hardware for my project to be available as standard off the shelf items.
I agree that 'simple' does relate to DOS and the ISA addressing mode.Things start to get a bit more complex when you move to the PCI bus and the windows plug and play system, but DOS is good at running these low level motion control routines. I refer to my previous post if a simple DOS machine will run the motors at Maximum speed how can a more powerful computer make them go faster.
If anybody wants to build arvid's board you can have the bits and I'll test it in my system.