I've been dabbling with SCSI quite a bit lately, and in my stash I found an Adaptec AHA-1542B card which I think suits older ISA-only machines quite well. However after installing it I encountered resource conflicts due to the fact that the default I/O port for the SCSI controller was 330h, same as the default port used by MPU-401 interfaces.

Changing the MPU-401 port was not a good idea since many older games are hard-coded to use 330h, so I attempted to change the port used by the Adaptec to some other value. The problem is that the BIOS only works when the port is set to 330h, so you lose the ability to boot from SCSI (I believe this was corrected on later models).

So, although I'm sure this could have been resolved in a different way, I decided the cleanest option in this case would be to patch the Adaptec BIOS to use another port. I chose 234h since it shouldn't conflict with the default I/O port range of other common hardware, but a similar patch could be produced to use any of the ports supported by the SCSI card configuration.

I am attaching the AHA-154xB BIOS ROM v3.20 patched to look for the controller on port 234h in case it is useful for other vogoners with one of these cards, it has worked perfectly for me so far but being a quick and dirty patch I cannot guarantee the absence of bugs. Just keep in mind the following if you intend to use it:

• Remember to set the jumpers on the SCSI card to use port 234h
• This is a patched version of the 3.20 BIOS, so it should go along with the 3.20 version of the microcode (also available online)