Welll...
Originally posted by Falleron
Can anyone give an educated estimate of how much faster this 1.8Ghz 970 will be when compared to Motorolas yet to come out 1.8Ghz G4?? What sort of percentages are we talking about? I dont want wishfull thinking figures. I want a realistic estimate.
Any ideas???
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Assume that SPEC scores scale linearly with clock frequency (which they don't, but it's easier to compare that way). A 1.8GHz G4+ would get 1.8x180 (roughly), or 344 on SPECFP. The 970 gets about 1050. The G4 would get about 540 on SPECINT, the 970 gets about 900 (note: SPEC is double precision heavy, and doesn't use Altivec). Why?
1) Memory bus bandwidth: 1.3GBps vs. 6.4GBps (about a 5x improvement)
2) Instruction dispatches per cycle: 3 (iirc) vs. 5 (close to a 2x improvement)
3) Floating point units: 1 vs 2 (2x improvement)
4) Out of order execution: none vs lots
5) Compiler: GCC vs IBM-übercompiler (whatever it's called)
6) 16 instructions "in flight" at one time vs. 40 groups of 5 (200)
7) the 970 has much more sophisticated branch prediction
I would expect the 970 to get close to double the floating point performance of a G4+ at the same clock frequency. Singly precision integer performance should be closer to equal. The 970 will be significantly ahead on double precision integer. For Altivec (VMX) code, I think the G4+ would have an edge over the 970, except that it doesn't have enough memory bandwidth (i.e. if you gave a 1.8GHz G4+ 6.4GBps of memory bandwidth, I think it would win at Altivec code).
I think it will average about 1.5-2x faster than a G4+ at the same clock frequency. I would also guess that it should be roughly equivalent in performance to Pentium 4s of the same time period (I'm guessing 3.6GHz, .09 micron, hyperthreading, 667MHz bus, >512k cache).