[aperezbios]

Now if I could only get my old HDDs to work too... the ST43400 _seriously_ acted up again as I was testing the CDROM, then came to life about 1/2 after tons of failed startups and SCSI bus resets. I have 3 of these bastards, and they all developed the same issue. But that's another story...

You might want to take a look at ZuluSCSI. It's a relatively new product (launched in May 2022) which supports synchronous SCSI, and incorporates SCSI2SD V6's SCSI command handling routines as a library. ZuluSCSI significantly less expensive than SCSI2SD V6, and can emulate up to seven SCSI devices at once, including CD-ROM. It uses a filename-based configuration mechanism, derived directly from BlueSCSI (The ZuluSCSI firmware is GPLv3-licensed, as is the BlueSCSI and SCSI2SD V5/V6 code base). It's incredibly easy to use, and may make those old ST43400 boat anchors a distant memory, as well as conserve a bunch of electrons in the process as well. 

The GitHub project page is at http://github.com/ZuluSCSI/ZuluSCSI-firmware and there's a ZuluSCSI web page at http://zuluscsi.com

Since you're in Switzerland, I'll send you a PM 

Full disclosure: I own Rabbit Hole Computing, which commissioned development of ZuluSCSI, as a response to critical semiconductor shortages, which have prevented us from being able to manufacture more SCSI2SD V6 and V5.2 boards. I've also had a bunch of SGI gear since long before SCSI emulators were an affordable thing, and had an account on Nekochan for a number of years.

In the interest of not hijacking this thread, please do not ask ZuluSCSI-specific questions here. Instead, I invite you to do so in a ZuluSCSI-specific thread, which I've just now created. Please feel free to participate at Introducing ZuluSCSI (irixnet.org)