Squaring the Overhead in RISC
Additionally, we also ran into an interesting result as we tried to move beyond 4-issue machines to 6 or 8 issue machines. The overhead that was placed on the chip's transistors just to keep track of what was going on when scheduling parallel operations increased exponentially as we increased linearly the number of functional units. Therefore, if you tried to move from a 4-issue to an 8-issue processor, the overhead did not increase by a factor of two—it increased by a factor of four!
From a RISC standpoint, this was an extremely frustrating and discouraging development. After all, what good did it do to try to increase the speed of a processor by adding more transistors if a greater and greater portion of the processing ...
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