I have an Intel Pentium 4 with Hyperthreading. The boinc client thinks I have two seperate CPUs. In my preferences, should I set my # of CPUs to 1, or is it ok treating my machine as a dual-processor?

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AFAIK, your hyperthreaded CPU acts like a dual-processor PC, so you can treat it like a dual-processor (or, in other words, 2 seperate CPUs), if you want to use all your CPU-Power for "number crunching", or treat it like a single-Processor, if you want to use 50% CPU power for crunching and the other 50% for "normal" work.

Greetings from Germany,

=Lupus=

No it is treating it like one real and one vitual CPU, and the Virtual will always lag behind the real CPU. Running both may get you any where from 10% to 60 increase in processing depending on project....

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BOINC Wiki

http://www.intel.com/business/bss/products/hyperthreading/overview.htm

The above URL will help answer your questions on why it shows as 2 CPU's. The Windows Operating system and I assume any Linux Operating system will show 2 CPU's on the system.

http://support.microsoft.com/default.aspx?scid=kb;en-us;896256

This URL will help make sure it actrally works for you in a Windows XP with SP2 Operating system.

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You'll notice that if you look at the Task Manager in Windows XP, under the TAB called "Performance" it shows 2 CPUs on a Hyperthreading Machine.

If you tell Rosetta to only use 1 CPU, then the graph in Task Manager will show both "CPUs" as using 50% of their capacity.

If you tell Rosetta to use 2 or more CPUs, then the graph in Task Manager will show both "CPUs" as using 100% of their capacity. Your BOINC client will also process 2 Rosetta work units simultaneously intead of just 1.

Hyperthreading will shove 2 seperate threads through your single CPU. Sometimes information from both can be processed in different parts of the CPU, other times it cannot and they make each other wait. The end result is, that you can process 2 work units simultaneously with Hyperthreading faster than you could process 2 work units one-by-one without it.

If you get a Dual Core CPU that will also show up as 2 CPUs. In this case, you will process 2 work units EXACTLY TWICE AS FAST as you would with only 1 non-hyperthreading CPU.

If you get a Dual Core CPU that also has Hyperthreading, your Task Manager will detect 4 CPUs, and you can process 4 work units simultaneously.

In order of speed:
non-HT CPU = 1 WU at a time = speed of 1.
HT CPU = 2 WUs at a time = speed between 1-2 depending on luck.
Dual Core CPU = 2 WUs at a time = speed of 2.
Dual Core HT CPU = 4 WUs at a time = speed of 2-4.