Author: Eugene Nalimov
Date: 20:45:17 03/26/02
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Of course cache will be NUMA; still, in the worst case it can be 3-5x faster than main memory. Let's take a look at the latencies of the not yet released CPU I am currently working with (from memory, so I can be slightly wrong): L1 1 clock cycle L2 5 clock cycles L3 12 clock cycles Main memory 180-225 clock cycles Assuming that non-local L3 access is 5x slower than local one it'll be 60 cycles. Much better than main memory. I agree that POWER4 is good processor, I just cannot believe it's so much better than others. Eugene On March 26, 2002 at 23:18:21, Robert Hyatt wrote: >On March 26, 2002 at 20:29:19, Eugene Nalimov wrote: > >>I would not trust POWER4 SPECint number too much. It was obtained at a multi-CPU >>system with shared L3 cache when all CPUs but one were idle, so that one CPU >>actually could use 16*8 == 128Mb of L3 cache. I doubt anybody ever will use >>similar system for single-process calculations. >> >>Eugene >> > > >The cache _must_ be NUMA however. There is no way to have a cache >with that many ports without degrading cycle time horrendously. I'll >bet there is much more to this that just a bigger cache issue... > > >> >>On March 26, 2002 at 17:24:45, Tom Kerrigan wrote: >> >>>On March 26, 2002 at 14:29:28, Vincent Diepeveen wrote: >>> >>>>If a 64 bits processor isn't faster than a 32 bits processor the processor >>>>is nothing more than a bad joke of course. >>> >>>Why is that? You might as well say any processor that's not the fastest in the >>>world is a bad joke. I don't see why the datapath width matters. And you're >>>saying "faster" now instead of "clocked higher." If you want to talk faster, the >>>POWER4 posts higher SPECint numbers than all current 32-bit processors. >>> >>>>>No matter how hard you backpedal, you're not going to get out of your idiot >>>>>statement that "not a single 64 bits processor is clocked *near* 32 bits >>>>>processors." >>>> >>>>I'm very right here. fastest 32 bits processor which i can buy is >>>>clocked at 2.4Ghz now. Fastest 64 bits processor (let's not even >>>>mention its insane price) is the power4 or something 1.3Ghz if >>>>i remember well? >>> >>>You said "32 bits processors," not the fastest 32-bit processor. The POWER4, at >>>1.3GHz, is most certainly clocked *near* (your word) the 1.7GHz Athlon, which is >>>a perfectly good 32-bit processor. >>> >>>-Tom
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