Re: Mersenne: Hyper-threading
- Original Message - From: Michael Vang [EMAIL PROTECTED] To: Daran [EMAIL PROTECTED]; [EMAIL PROTECTED] Sent: Sunday, September 22, 2002 12:19 AM Subject: Re: Mersenne: Hyper-threading Look towards the end of this thread for benchmarks with LL and factoring on one processor via hyperthreading... http://www.teamprimerib.com/gimps/viewtopic.php?t=8 Thanks Mike (Xyzzy) Daran G. _ Unsubscribe list info -- http://www.ndatech.com/mersenne/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers
Mersenne: Hyper-threading
Could this feature of forthcoming Intel processors be used to do trial factorisation without adversely impacting upon a simultaneous LL? Could this be easily implemented? Regards Daran G. _ Unsubscribe list info -- http://www.ndatech.com/mersenne/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers
Re: Mersenne: Hyper-threading
Daran wrote: Could this feature of forthcoming Intel processors be used to do trial factorisation without adversely impacting upon a simultaneous LL? This was discussed in March, starting in Digest Number 945. Short answer: no. Medium answer: If an application were not already optimized for maximum pipelining, hyperthreading would allow another application to use unused pipeline capacity. But Prime95 is already so optimized. Richard Woods _ Unsubscribe list info -- http://www.ndatech.com/mersenne/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers
Re: Mersenne: Hyper-threading
On Saturday 21 September 2002 21:20, Daran wrote: Could this feature of forthcoming Intel processors be used to do trial factorisation without adversely impacting upon a simultaneous LL? Could this be easily implemented? 1) _Existing_ Pentium 4 Xeons have hyperthreading capability. 2) Implementation is easy; just run two processes - one LL one TF - assigning one to each virtual processor. In fact there's no other way to implement: you can't have one process running in multiple virtual processors simultaneously with hyperthreading technology alone. 3) I reckon there would be a very significant performance hit. Temporary registers, instruction decoders etc. are shared so any pressure whatsoever on the critical path would cause a performance drop - even if the code in the two processes could be guaranteed to stay phase locked so that there was no simultaneous call on a particular execution unit. (In practise I think unregulated phase drifts would result in a phase locked clash, since this appears to be the most stable state). You would probably get 20-30% more _total_ throughput this way than you would be running LL DC assignments in series, i.e. the LL test speed would be at best 2/3 of what it would be without TF running in parallel on the same CPU. One benefit of hyperthreading technology for compute-bound processes in an interactive environment - provided you're running only one compute-bound process per _physical_ processor - is that the extra capacity helps the system to react more quickly to interactive loads, so it's a lot less likely that foreground users will notice the background CPU load. Regards Brian Beesley _ Unsubscribe list info -- http://www.ndatech.com/mersenne/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers
Re: Mersenne: Hyper-threading
Look towards the end of this thread for benchmarks with LL and factoring on one processor via hyperthreading... http://www.teamprimerib.com/gimps/viewtopic.php?t=8 Mike (Xyzzy) _ Unsubscribe list info -- http://www.ndatech.com/mersenne/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers
Mersenne: Hyper-threading
Found this article on News.com about the new Pentium 4's coming out next year... code-named Prescott. It mentions a speed of 4GHz... and the use of hyper-threading... Hyper-threading is supposed to allow two applications or application threads to run on one processor at the same time... by allowing one application (or thread) to use parts of the processor it needs... and the second application (or thread) to use others... Esentially this could speed up testing even more... by having one thread of Prime95 use the FPU... while another uses the IAU... The article also mentions AMD's Clawhammer due out the end of this year... able to run 64-bit applications... This could significantly reduce the number of adds/multiplies required for testing _ Unsubscribe list info -- http://www.ndatech.com/mersenne/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers
