Re:The Art of Picking Intel Registers (2003)
by caf on Sunday April 22, 2018 @11:41PM
(#16900361)
It's not so much the registers themselves, it's the plumbing required if you're going to let any register supply any input or output of the ALU. Hardwiring a register to one of the ALU's ports means you avoid a multiplexer (and the same applies to hardwiring a register to the AGU's ports, which is how you get 'base' and 'index' type registers).
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Sure, there are lots and lots of deeper details but fundamentally, more registers means more transistors (or a higher-level logical unit of choice) and it's the constraint that drives accumulator-centric designs, specialized registers, etc. Relax the constraint and they become less necessary.