Re: Mersenne: 50% CPU?

[ModularTao]

In a message dated 11/3/2003 2:43:30 PM Eastern Standard Time, [EMAIL PROTECTED] writes: Does your CPU have hyper-threading for sure, and it's enabled in the BIOS? Task Manager will show one graph per CPU... If you only see a single graph, your OS only thinks it has one CPU (counting all virtual and all real CPUs). I also assume you're using WinNT/Win2k/WinXP since Win98/ME doesn't support multiple CPU's (and doesn't really have Task Manager either...just that system resources thing). Check your list of running processes and see how many Prime95's show up. Should just be 1.  If you have 2 running, yeah, running 2 processes on a single CPU, even with the multi-threading, will generally hamper how well either one runs. I once toyed with the idea of running LL tests on the real CPU and running factoring tests on the virtual one, but I never could decide if that was helping out at all...My gut tells me no just because of the memory accesses and not using the single L1/L2 caches on the CPU as well as they could be. By the way, that's a sight to behold when you have a quad CPU P4 system... 8 graphs happily bouncing away.  I'm sure on an 8 CPU system it must be terribly impressive to have 16 graphs showing up, but I've yet to get my hands on such a system. :)   Thanks very much for the information - my configuration must be to treat any virtual CPU as part of the physical one since there is only one graph; (unfortunately for the nice visuals - 16 would be lovely and probably hypnotic!).    I double checked and there is only one instance of Prime 95 running - on my older Pentium 3 I had played around with running two copies but the interation times were approxiamtely 3 times longer for each than 1 running solo - haven't tried it yet on this machine but my impression is the same as yours - there wouldn't be much, if any, benefit but it might be fun to play around with :-).