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Double Processor HT

Questions and Answers : Getting started : Double Processor HT
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Yeti
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Message 21 - Posted: 5 Aug 2004, 14:35:00 UTC

Hi,

my box has an Intel P4 with Hyperthreading.

If I allow in my profile \"use 2 Prozessors\", will the client run ONE simulation with both prozessors or will the client run 2 different simulations ?
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Profile Honza
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Message 24 - Posted: 5 Aug 2004, 14:46:21 UTC

Hi Yeti,

there is no way (so far) to use multiple CPUs on a single model -> each CPU is simulating different model.
You can get some +15% on P4 HT but keep in mind that it need another 50-60MB of RAM, HD space etc.
You may also find interesting running single BOINC model and keep your 'classic' CPDN/Win running another; assuming you are on Win platform.
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Message 104 - Posted: 5 Aug 2004, 19:53:26 UTC - in response to Message 24.  

Hi, as Honza says it will be one workunit per CPU (I believe all BOINC projects behave this way, not just CPDN).

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Message 106 - Posted: 5 Aug 2004, 19:57:08 UTC

Yeah, as you prognosted: My workstation is crunching two modells now ...

Thanks four your help :-)
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Message 961 - Posted: 14 Aug 2004, 9:19:11 UTC
Last modified: 14 Aug 2004, 9:23:27 UTC

There was a lot of debate (on the BOINC beta board and elsewhere) about the > 1 cpu/2 cpu/ HT

The conclusion that I came to was that there was little benefit from running HT so I switched it off on my intel P4 3.06 PC and set my Prefs to 1 cpu for this PC.

The situation may be different for AMD cpu's.

K.

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Message 964 - Posted: 14 Aug 2004, 9:44:32 UTC - in response to Message 961.  

> The situation may be different for AMD cpu's.

actually my experience is that HT is pretty good on these climate models -- you lose a little bit "seconds per timestep" but you get two models done in a little bit extra time (so your "model throughput" is almost halved, i.e. you effectively are doing a model every 10 days instead of 18 days or whatever)
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Message 965 - Posted: 14 Aug 2004, 10:18:11 UTC - in response to Message 961.  

> There was a lot of debate (on the BOINC beta board and elsewhere) about the
> > 1 cpu/2 cpu/ HT
>
> The conclusion that I came to was that there was little benefit from running
> HT so I switched it off on my intel P4 3.06 PC and set my Prefs to 1 cpu for
> this PC.
>
> The situation may be different for AMD cpu's.
>
> K.
>
>
>


I'm running a P4 3.0E 512Mb DDR800 PC3200 with HT and am getting;
Model 1, 3.01 s/TS
Model 2, 3.12 s/TS
It should take me 28 cpu days to complete 2 models, from looking at other
P4 3.0E cpu's with HT off it should take on average 33 cpu days to complete
2 models.
Thats 5 days faster for 2 models but thats guessing at this point and we will
have to wait and see.
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Questions and Answers : Getting started : Double Processor HT

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