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Risc vs Symbolics (was: Poor Sun timings, as competition...)
Date: Mon, 13 Aug 90 16:50 EDT
I know that real users compare whole systems (i.e. hw+so+compiler+env.+...)
but i was wandering if someone has tried to answer to the following
I don't think it is a silly question.
My gut feel is that you'd need at least a factor of 3 and 4 to break
even, though you'd have to do the architectural design and then code up sample
frequent instruction sequences and sum their timings to be sure.
I'd rate this another way: I'd say it would take about a 50%-100% larger
factor than the usual CISC:RISC break-even ratio. That's my feel for
how often the Symbolics architectures' parallel paths save cycles for
Also, the storage of tags is a problem; if you want 32-bit integers and floating
point numbers, but also want tags, you must have either a word size bigger than
32 bits (Ivory has 40) or do some kludging around to simulate it which will no
doubt have a negative impact on the performance of most if not all memory
It should be pointed out that Genera depends on being able to do
fixnum arithmetic on addresses in a few places.