I was just wondering if it is possiable to combine the power of all CPU's available to process one work unit (either for HT or Dual Core or even both)?


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I don't own one , I don't have own experience, I only read here in the fora from guys/gals who owned/had that it will not improve you output but will worsen it. Even on HT with only virtual 2 CPU the output of two WUs crunched simultaniously is higher then the output of of only one at the time. It's not double afaik but ~1,7x, but nevertheless.

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Gruesse vom Saenger

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I was just wondering if it is possiable to combine the power of all CPU's available to process one work unit (either for HT or Dual Core or even both)?

No

I don't own one , I don't have own experience, I only read here in the fora from guys/gals who owned/had that it will not improve you output but will worsen it. Even on HT with only virtual 2 CPU the output of two WUs crunched simultaniously is higher then the output of of only one at the time. It's not double afaik but ~1,7x, but nevertheless.

Who said this? The output with 2 cpu's _is_ higher than with 1 cpu (ht or dual core or real cpu)

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I don't own one , I don't have own experience, I only read here in the fora from guys/gals who owned/had that it will not improve you output but will worsen it. Even on HT with only virtual 2 CPU the output of two WUs crunched simultaniously is higher then the output of of only one at the time. It's not double afaik but ~1,7x, but nevertheless.

Who said this? The output with 2 cpu's _is_ higher than with 1 cpu (ht or dual core or real cpu)

Isn't that just what I said? It's just not double the outcome on a HT, but significantly more.

I only read here in the fora from guys/gals who owned/had that it will not improve you output but will worsen it.

This means that the output will be worse on 2 cpu (or was i misunderstanding?)

Even on HT with only virtual 2 CPU the output of two WUs crunched simultaniously is higher then the output of of only one at the time. It's not double afaik but ~1,7x, but nevertheless.

Isn't that just what I said? It's just not double the outcome on a HT, but significantly more.

i only read the beginning and thats why i answered.
on ht it depends on memory, cache etc... i have machines where the output on ht is only 30% more than without and some are about 80% more.
and no dual machine doubles really the power, that is correct. there is always a loss of minimum 10%.

regards

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I only read here in the fora from guys/gals who owned/had that it will not improve you output but will worsen it.

This means that the output will be worse on 2 cpu (or was i misunderstanding?)

I understood his question this way: If I combine my (virtual) CPUs to crunch only on 1 WU, will it improve my processing somehow?
And to this question I answered: No, it will worsen.

But I see, we both have the same answer for this question, whatever was asked ;)
Happy crunching!

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Gruesse vom Saenger

For questions about Boinc look in the BOINC-Wiki

As a side to this discussion, if you already have Hyper Threading enabled, you would have to disable it in the BIOS and reinsatll XP from scratch. You're not likely to see better performance from crunching one WU at a time as stated befroe.

A multi-threaded science application could be nice, but I'm not sure the work that has to be done allows for it.

In my opinion, on hyperthreaded systems, it could potentially reduce cache-contention between two seperately running results, because both virtual cpu's would be working on the same dataset, however, on multi-cpu-systems it would require synchronizing the cache of both physical cpu's on a regular basis, which would introduce some delay in the processing.
It would also involve a serious rethink of which dependencies exist in the way the calculations on the data are ordered.
In my opinion, it would be a nice exercise for the programmers of the science application, but I have some reservation as to the possible gains in total processing throughput on most systems.

As a side to this discussion, if you already have Hyper Threading enabled, you would have to disable it in the BIOS and reinsatll XP from scratch. You're not likely to see better performance from crunching one WU at a time as stated befroe.

This is incorrect. The multi-processor HAL is 'plug & play' with respect to adding or removing processors. You can enable/disable Hyperthreading, or add/remove a processor at will without having to reinstall. All that's required is a reboot.

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As a side to this discussion, if you already have Hyper Threading enabled, you would have to disable it in the BIOS and reinsatll XP from scratch. You're not likely to see better performance from crunching one WU at a time as stated befroe.

there is a performance boost on ht systems if you only crunch 1 wu, even if you don't disable ht and don't reinstall xp (or 2k). on classic this was from 20% to 80% depending on hardware. the little overhead of 2 cpu support should only take 1% of overall power, not more.

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As a side to this discussion, if you already have Hyper Threading enabled, you would have to disable it in the BIOS and reinsatll XP from scratch. You're not likely to see better performance from crunching one WU at a time as stated befroe.

This is incorrect. The multi-processor HAL is 'plug & play' with respect to adding or removing processors. You can enable/disable Hyperthreading, or add/remove a processor at will without having to reinstall. All that's required is a reboot.

While you could just do that, when Windoze is loaded on a HT enabled PC, it loads more files in order to use those capabilities. If you just simply turn off HT, those files are still loaded imposing a performance penalty.