Author: Thomas Mayer
Date: 17:43:05 02/08/04
Go up one level in this thread
Hi Sune, > I don't like the comparison at aceshardware, they compare nps directly > between Diep on the Athlon with one thread and the P4 with two threads. > I think they should have mentioned that the efficiency of the extra thread > isn't 100%. > So I'm left asking, "What does the test show?" and "How much faster is the > Athlon for Diep?". well, that's simple math: I don't have the numbers of acehardware in mind anymore, but let's make an example: Think that we have 2 Threads producing 200 knps. Now we device that through the number of threads and get 100 knps... Multiplicate that with a guessed efficiency of - hm - let's say a conservative 1.7. Now we have 170 knps. So in comparison 200 knps with 2 Threads would be equal to 170 knps on a single CPU. So you can do now the same thing with the numbers at acehardware. For hyperthreading we can now even create a formula how much speed up in nps would be needed to have some payback for the hyperthreading: (1+s)/2 * 1.7 > 1 (s is speedup in %) 1+s > 2/1.7 s > 2/1.7-1 s > ~ 17.6 % So with a efficiency of 1.7 you must get more then 17.6% speedup in nps because of hyperthreading that you have some payback. If the efficiency is better, let's say 1.8: s > 2/1.8 - 1 s > ~ 11.1 % So with a efficiency of 1.8 a speedup of 11.1% would be already enough. I hope I have not done to much wrong mathematic stuff above -> it's long time ago I did it... :) Greets, Thomas
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