I picked up a ST351A/X hard drive which has an 8 bit mode to see if I could get it working with an Innerdrive card.
I set the jumpers for 8 bit, the drive spins up and kerchuffs when I start up the IIgs. The utilities disk is GSOS and stops halfway through the boot. Unfortunately the only utilities I’ve seen are GSOS.
I formatted the drive with the MicroDrive Turbo and Vulcan cards but the formatting is different from the Innerdrive cards. So I know the card, cable and drive are working, just not together. I’m wondering if the Innerdrive cards ROM might only allow it to work with WD hard drives. I can’t think of anything more I can do at this point.
On the good side I found another hard drive that will work natively with the Vulcan.
I remember having issues with the ST-351A/X in 8-bit mode on the CDrive. It uses virtually the same code as the Inner/Outer Drive. Seems like it should work but there was some difference.
You should be able to get it working with an ST-325X if you can find one.
I'll keep an eye out for a ST-325X but they’re getting into the hens teeth category now.
Is there anything special about the ST-325X? I mean it's just an IDE drive, right, albeit 8-bit only? Could a CF card IDE adapter be used in its place?
Technically, yes. But these early Apple II hard drive solutions had storage size and geometry hard coded into the firmware. I did an update to the CDrive that worked with CF card (IDEA2C) but the card needed a specific formatting. It worked with existing CF cards for the MicroDrive Turbo but that formatting utility also would have needed modification.
The InnerDrive did work with 4 different geometries:
20MB 17 sector, 4 head, 615 track
20MB 27 sector, 2 head, 782 track
30MB 27 sector, 3 head, 782 track
40MB 27 sector, 4 head, 782 track
so it's possible there are other drives out there that could work.