What exactly is a rotating register Someone said the term to me but I had no idea what they meant be it.

Any description/links would be appreciated.

Cheers, pal.

In what context was it said? It is hard to know what it means without the context.

Maybe to rotate the bits within a register via ror or rol?

I thought it was about literally rotating the registers using rol/ror/rcr/rcl but I'm not sure.

I'll try to get the person to explain what he means, but he literally said to me "Do you know what rotating registers are?". I thought of the rotating instruction mnemonics too. The only thing that I found relating to it is:



But it doesn't really explain much to be honest. I'll find out more when I speak to the guy again.

This is what he said:



He then said he wasn't listening though so I don't really know.

Perhaps a different way of saying this?

ROTATING REGISTERS:
THe same rules are for different register sizes.



ROR - Rotate right:






ROL - Rotate left:






RCR - Rotate right with carry:






RCL - Rotate left with carry:






For more information go on wikipedia

Pirata Derek: I think "rotating" is used as an adjective, not as a verb. But thanks for the pretty pics anyway.

It probably means like the x86 FPU except that it "overflows" back to the original st0 register if you go over once it's full.

Nice pictures, but yeah I don't think it was that. I have to wait for him to come back on to see if he can explain it again.

Borsuc: that was another thing I thought of, the FPU style registers.

OK Madis cleared it up for me. The rotating registers are from Itanium architecture, not Intel.

IA64 does have 128 FPU and 128 CPU registers. Nothing new there. It also has a hardware supported register windowing facility - that could be the rotating register thing. But who knows, could be anything else also.

Anyhow, if you want to learn more about the (dead) IA64 architecture search for Itanium (and/or IA64 of course).

Yeah my bad. The guy who said it to me didn't mention the IA-64 bit originally but said 64-bits, so I assumed he was using x86-64 bit. Either way I didn't know about IA-64 like that. Cheers all.

Let's not forget that it could be a reference to alternate registers (the idea that there are more registers that we can access, but to reduce hardware restrictions, the registers we specify are aliased).