The XTIDE universal bios will happily support 16-bit ISA IDE controllers. You don’t need to use a dedicated XT-IDE card.

You are describing the common I/O card that all computers without an onboard IDE controller had since the 286. I probably don't understand something here.

paradigital wrote on 2024-02-03, 17:49:

The XTIDE universal bios will happily support 16-bit ISA IDE controllers. You don’t need to use a dedicated XT-IDE card.

Yes, but OP only has a single ISA slot and a broken onboard IDE controller. Short of using an ISA riser or an expansion chassis, it is in feasible to have the XT-IDE BIOS in one slot and an IDE controller in another .

konc wrote on 2024-02-03, 18:20:

You are describing the common I/O card that all computers without an onboard IDE controller had since the 286. I probably don't understand something here.

OP asked about a 16-bit IDE controller with on option ROM onboard (to load XT-IDE from)

While 'unpleasant', the XT-IDE bios can be loaded from a floppy diskette.

More info:

A tool like this one can be 'booted', which copies an option rom, (which XT-IDE happens to be) into system memory, then executes it.

Bootable ROM loader floppy

The kids at VCF played around with doing exactly that.

https://forum.vcfed.org/index.php?threads/xt- … of-eprom.53245/

As for ISA IDE controllers with option ROMs... just junky Promise controllers, are all I really remember.

Edit:

Like this one.

https://www.ebay.com/itm/234886840736

Caveat emptor on that floppymax though. Either play doctor on it (Promise FloppyMAX converted to primary or secondary IDE interface) or look for an EIDEMAX.

darry wrote on 2024-02-03, 18:22:

konc wrote on 2024-02-03, 18:20:

You are describing the common I/O card that all computers without an onboard IDE controller had since the 286. I probably don't understand something here.

OP asked about a 16-bit IDE controller with on option ROM onboard (to load XT-IDE from)

Ah so that's what I missed, thanks. It's not clear because for what he wants to achieve (connect a 40MB HDD and a CF) it's not needed, if you exclude the BIOS HDD size limits.

Replacing the dodgy (optional! It can be disabled!) Option rom on a promise card might work for them.

Presumably, they need a bios routine to set up the hard disk interrupt vector table entries, so DOS will actually see and use the drives.

Thanks everyone, some helpful ideas and am super grateful for the pointers.

I am still diagnosing the fault with the onboard controller and i think i have ruled out the connections to it but not certain as yet. All my old ISA hardware has long since been passed on but i liked the idea of the combined CF flash reader with the onboard IDE controller i found here which could be loaded with the universal bios. If i fail with the repair, my understanding is that with the right CF card installed and jumpered as a slave to the original 40MB HDD, i may get the system to boot into Win3.1 and recover my old files and really kick the nostalgia into high gear!

Cheers
Pops