Karl Townsend wrote:

Off hand do you recall which IRQ and memory address did you use?

LPT1 (built in) is at the normal 0x0378
LPT2 is at 0xDD00
LPT3 is at 0xDF00

All three are set to "never use an interrupt".

I use another PC control I'm really surprised you don't use an interrupt
with Mach. My control has an IO card that fires an interrupt if an input
changes state. The computer then polls for which input changed. How does
Mach trigger an event on an input change?

Karl

There aren't that many inputs and Mach has no problem polling them at an
acceptable pace. A multi GHz CPU doesn't spend much time reading and
comparing a few port addresses. I don't know the exact details, but I
expect the Mach pulsing driver probably collects the input status data
on each output update cycle which could readily be 120KHz. Hardware
interrupts are largely a barnacle from the days of 1MHz CPUs.