Quoting Jim Leonard <trixter at oldskool.org>:
This reminds me -- what's a good 8-bit SCSI
adapter for IBM PC 5150-class
machines? I've got SCSI drives here that I'd like to put to use, but all I
have for this machine is a Western Digital MFM controller.
Future Domain 8xx series. Some are bootable, some are not .. do a wee bit of
research first. Some also have non-standard connectors on the back, so they
should be avoided.
These are known to work on a PCjr with an ISA bus adapter. (Software only -
I've not fixed the ROM extension to give it native BIOS support on the Jr.)