Émeric Maschino blazed a trail:

   Just to let you know that AIX 1.3 for PS/2 boots fine from the
original 270MB IDE HDD in my PS/2 Model 76i. No need to boot from
diskettes, as rumored by several posts on this newsgroup  ;-) 

At first, AIX can't be installed at all because of the Convenience
Partition. The installation process was looping between the "Install a
new AIX system" option menu and the "Removing all AIX minidisks..."
message. But once the Convenience Partition was deleted, no more
problem. I didn't find an evidence of this issue on the various posts
and AIX documentation. Did I miss it?

The AIX installation process ran with the 3 PTF0024 boot and
installation diskettes, and then the 15 GA BOS diskettes. The PTF0024
boot diskettes were needed once more time to boot the system and run
it from the IDE HDD. PTF0024 APAR U436295 was then installed. A new
kernel was rebuilt allowing AIX to boot from the IDE HDD.

Next objective is to install OS/2 2.1 on the same HDD and have a dual-
boot AIX-OS/2 system. Too bad that AIX eats two primary partitions:
ideally, I would like to have one more available for PC-DOS 5.0 and
play with DOS Merge. Unfortunately, a second HDD isn't an option, as
there isn't enough room for that on a PS/2 Model 76i sported an
internal IDE CD-ROM drive. Oh yes, and there's also this issue with
the 3c529 NIC under AIX. Will I be more lucky than others? Heh, I
didn't have a problem to boot from a IDE HDD after all, so there's a
little hope!