Seems plausible to me - BIOS may be too old to support ATAPI anything (and doesn't have to, compare to how you're supposed to disable the HDD there if you use XTIDE universal bios or the like), El Torito for bootable CDs was invented rather later (1995 - for the theoretical standard only), and still needed multiple years (give or take, Pentium 3 launch) to become ubiquitous, never mind actually working in all the floppy/disk/no-emulation-with-2048-byte-sectors variants...

Yep indeed seems it’s still in era which requires a dos sys file install then the CDROM driver off the floppy.

Worked first time. Now just the challenge of getting the mouse working.

Andy223uk wrote on 2023-07-20, 21:50:

seems it’s still in era which requires a dos sys file install then the CDROM driver

Just a nitpick - even if your BIOS supported CDs and direct successors, you'd still need a specific* CD driver for the operating systems, unlike HDDs which got hacked into the originally floppy-only int13 there's usually no provision# for general CD reads via ROM-provided code...

* Sure, nowadays it's no early 90s jungle and a generic ATAPI CD driver like OakCDROM or FreeDOS's UIDE, never mind built-in support in Win32/Linux/etc, goes a long way if that's what you have!

# Actually, there's an ELTORITO driver by the famous Bart which does exactly that, but it only applies to bootable CDs that were booted by the BIOS, and still needs a "light" loadable driver in config.sys + an ISO9660 driver like MSCDEX 😀