I remember we had these in Acorn machines, when I was at school in the 90s (in the U.K.). They were always very fast I remember. They were replaced with PCs later on, but due to the budget the school was on, these ending up being much slower at the time but that was most likely due to Windows needing a lot more memory than RISC OS did.

ARM did originally stand for Acorn RISC Machine, so it makes perfect sense that your Acorn machines had ARM processors :).

They were fast, but they were not necessarily faster than x86 machines. They were RISC compared to CISC(old x86), so hard to compare them directly.

I'm pretty sure it was to do with the RISC OS being lightweight memory wise than anything. I had some good spec'ed PCs at that time but those relatively cheap Acorn machines were always faster in basic OS tasks.

As far as I recall, at least part of that was down to hardware acceleration.

They were still awesome machines, though. Fantastic for learning assembler on.