i've seen a few isa multi-io cards with 2 ide ports, probably with the umc8663 chipset.
do they comply with eide standard and need any bios support to work with 4 drives? would they ever work with a 386 mainboard, or for isa 486 boards only?
Just installed an UMC UM8663 controller one a week ago on a 386. They work just fine on standard pc's (with 4 drives). No bios support is necessary. It does not support EIDE though. But depending on BIOS/XT-IDE/OS etc you can use larger HDDs without issues.
I mentioned standard pc's as some pc's have integrated controllers (which sometimes cannot be disabled) or use resources which can conflict with the secondary IDE port. Never came across one but they do exist.
I don't think they need any special BIOS support. It might have jumpers for setting these(for co-existence with other IDE controllers) but likely it offers up primary controller at 1F0h and secondary at 170h.
Also check out the Promise EIDEPRO, 16-bit multi I/O with two EIDE and option ROM to support.
Connecting hard drives to the primary and CD-ROM drives to the secondary wouldn't require any special support. Your ATAPI CD-ROM .SYS driver knows to probe 17x/37x without going through the BIOS.
Connecting hard drives to the secondary is either going to require BIOS support, overlay software or XT-IDE Universal BIOS, or a DOS .SYS file to see the secondary drives.
Random read/write speeds are the slowest hard disk function and can be improved with a CF card, if you want max hard disk speed. Not sure EIDE cards are a benefit unless you're transferring large files.
MikeSG wrote on 2026-07-24, 07:46:Random read/write speeds are the slowest hard disk function and can be improved with a CF card, if you want max hard disk speed. Not sure EIDE cards are a benefit unless you're transferring large files.
i don't expect isa ide cards to be any fast, even the fastest isa video cards run at about 4mb/s. all i want is stuffing more 500mb ssd drives into it.
