I don't think it uses one at all. Mine has no configuration jumpers or anything for it...

r.cade wrote:

I don't think it uses one at all. Mine has no configuration jumpers or anything for it...

So it uses polling instead of IRQ in an XT? Interesting....

The XTIDE BIOS has a menu option for specifying an IRQ between 2 and 15 so it must be able to use it. My question is what is the default...

No DMA support = no IRQ needed.

I don't know if it's actually "polling" but it's a simple interface. The idea was that the performance of the drive far outweighed ignoring those features for simplicity, and it's still comparable in speed to the old MFM interfaces.

vladstamate wrote:

The XTIDE BIOS has a menu option for specifying an IRQ between 2 and 15 so it must be able to use it. My question is what is the default...

Must it? 😀

I think that may be for newer cards or different designs that are XT-IDE compatible... v2/v3.

But if you're talking about the original XT-IDE, I'm pretty sure it's lacking hardware support for DMA/IRQ.

If I recall right on most XT is was IRQ 2 or 5 depend the setup
8 bit bus computers (8086/8088 based XT type)
IRQ Used for
0 Ram Refresh & Clock Tick
1 Keyboard Interface
2 EGA / VGA Video (some other interface controller cards have the option of using this IRQ)
3 COM2 / COM4
4 COM1 / COM3
5 Hard Disk Controller
6 Floppy Disk
7 Parallel Printer Port LPT 1

Just to close the loop on this. You were right, there is no IRQ required or operation in either XT-IDE or AT-IDE bioses. I managed to emulate them and for XT there is no handler and for AT the 14 and 15 IRQs are masked out during operation, so I assume the XTIDE (AT) bios just does not use them.