At 00:39 06.07.00 -0700, Dennis Peter wrote:
>#1: I have a dual processor BP6 motherboard running 2 Intel Celeron 433Mhz
>processors. I have 2 instances to GIMPS running and everything works OK.
>When I close ONE of the instances, the other remaining GIMPS instance runs
>*faster*. Can someone please explain that phenomenon to me? Why would it
>run faster? It still takes 50% CPU cycle in my task manager.
Most likely, the problem here is getting fast access to memory. When both
CPUs are working as fast as they can, the bottleneck is probably that the
memory bus is full (or whatever you call it :-) ).
>#2: I understand that GIMPS uses the FFT algorithm to do rapid modulo
>multiplication. Is it possible (or even feasible) to split that atomic FFT
>task and make it multithreaded to utilize both CPUs in my computer? Would
>it improve performance? Would it even make sense?
This has been discussed earlier on the list (see the archives for an
in-depth discussion), and the conclusion was: Yes, in theory, it's
possible, but you'd require extremely fast communication between the CPUs
somehow, and it would really be much more trouble than it's worth. It
depends a bit on how the L2 cache is -- shared or not. Or perhaps I just
remember wrong again, but at least there are people on this list to correct
me ;-)
/* Steinar */
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