I never ran QNX, but my experience with BeOS were similar to yours in that a Pentium 90 felt great!

Another data point:

SGI IRIX has an unusually good scheduler. I ran a 30Mhz machine for a while and it's desktop was pretty snappy.

One day, I compiled AMP and fed it a list of .mp3 files, most being 192kbps. The program could decode 256kbps without skipping, just FYI.

Those files were on an NFS share.

When I ran the gr_osview program, CPU was 95 percent utilized, and still the file manager was responsive and that music did not skip.

Frankly, just decoding higher bitrate > 192kbps mp3 files at 30Mhz was impressive.

Doing it with a full X Window system desktop, while playing he files off an NFS share, while remaining responsive speaks to a lean and mean network stack and scheduler that performed even on low spec hardware.

Was IRIX 5.3 FYI. Indigo Elan

A friend and I enjoyed operating systems and ran Be on an old Pentium 90, and like the parent comment says, it was snappy!

Linux also has a part in this:

After a water event, that Pentium 90 was no longer reliable. Used non parity RAM and Windows NT would go slowly senile eventually blue screening over and over.

For funzies, we put Red Hat 5.2 on that box and it ran fine! The syllog had a bunch of entries every second too. Open X console, and just watch them go by...

That box served up the company web page for a coupla weeks just for fun too.

Good times.