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Why 64 bit?
Why 64 bit?
Posted Sep 13, 2006 15:34 UTC (Wed) by charris (subscriber, #13263)In reply to: Why 64 bit? by TwoTimeGrime
Parent article: What you should (and shouldn't) expect from 64-bit Linux (Linux.com)
I haven't noticed much difference on the desktop, but for certain numerical things there can be significant differences. For instance, the random number generator MWC8222 relies on multiplying two 32 bit integers with a 64 bit result and runs about twice as fast on amd64. Oddly enough, that advantage disappeared on the emt64 xeon machine I tried it on, so go figure.
By and large I am favoring 32 bits for the short term just because of the codecs and such. When those things eventually mature, and with MS in the 64 bit desktop market they will, I will switch over for good.
Chuck
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Why 64 bit?
Posted Sep 13, 2006 17:29 UTC (Wed) by zlynx (subscriber, #2285) [Link]
Now, this may not be factual, but I have read that Intel cheated a bit with EMT-64 instructions.
What they apparently do is run 64-bit operations through their existing 32-bit ALU, and because their P4 architecture has a double-clocked ALU, this isn't so bad. What it does mean though, is that you've just exchanged the instructions a 32-bit compiler generates for 64-bit ops with CPU microcode doing the same thing.
Why 64 bit?
Posted Sep 14, 2006 6:57 UTC (Thu) by khim (subscriber, #9252) [Link]
It's not the same thing. 64-bit instructions were discowered in the photo of Prescott CPU two years before Intel said that he'll support EM64T! How ? On the photo you can find TWO 32bit ALUs! One is used for 32bit, another one - for high half of the 64bit (it's smaller, it's registers don't have tags so can not be used separately, etc). It means that while it's slower then AMD64 it's still faster then what the compiler does - because the compiler can only use first ALU!