Re:How the Z80's registers are implemented
by Animats on Sunday October 05, 2014 @04:59PM
(#8413431)
It's cool seeing register renaming in an early microprocessor. Doubling up all the registers takes a lot of silicon, and is unusual for that era.
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Re:How the Z80's registers are implemented
by userbinator on Sunday October 05, 2014 @08:38PM
(#8413910)
I don't know if the term "register renaming" was even around at the time since the other instructions (e.g. MOVs) don't "rename" registers, but they certainly had the right idea - "why move the data around when you can just change the register selection bits?" It's also how I expected the exchange instructions to work when I first saw the instruction set and the timings, so it's probably a rather natural and obvious way of doing it.
I did it the same way when I designed a Z80-compatible CPU in a (graphical) logic simulator, although I used a dual-ported register file.