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Old 21st May 2006, 7:52 pm   #69
YC-156
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Join Date: May 2005
Location: Aarhus, Denmark
Posts: 281
Default Re: PC as a standard convertor

Quote:
Originally Posted by Sean Williams
Does anyone know if I could use a twin processor unit for this purpose - there are some fairly well specd models on Ebay at present, and at a reasonable price, located a few miles from me - any ideas?
Well, I haven't used MythTV for ages, but I did look into this idea a while back when Kat's results first emerged. This because I presently happen to have two dual processor machines here at home.

What I found was:

*) The MythTV documentation doesn't mention SMP (Symmetric MultiProcessor) with even a single word when it comes to hardware selection. In my experience this means that the program will not utilize two processors at once, if present. So if a single, slow CPU cannot encode/decode as fast as one would like, two of them will not be of any help.

*) Some people on the MythTV reported driver problems when running SMP. Ie. the drivers were not thread safe. Not good.

So unless you need to run two CPU intensive programs at once while running MythTV, SMP probably won't help much.

Additionally my experience with using SMP machines as workstations and number crunchers are that with older hardware you usually run out of other resources before the CPU power is exhausted. Ie. harddisk, memory or DMA speed is insufficient to fully saturate two CPUs. The exception is very CPU bound applications like raytracing, where you often can run two tracing instances at once for close to a 100% speed advantage.

SMP may help when you need to run two dissimilar programs at once. Like if something happens in the background while MythTV is playing, a second CPU might help prevent 'stuttering'. Notice emphasis on 'might'.

When the program of interest really is limited by the CPU, a single slightly faster CPU is often way ahead of two relatively similar processors at half speed or so. This is due to all the other enhancements, which accompagnies the faster CPU/motherboard. As an example of this, then a single 1GHz P-III is so much faster than 2x 400MHz P-IIs that it isn't even funny. The P-III has a larger cache, faster RAM interface and other architectural enhancements, so it is way faster than twice the combined CPU horsepower of the P-IIs.

Another case I have personally experienced was a single 1.3GHz P-III 'Tualatin', which obliterated a pair of 550MHz P-III Xeons! The latter pair was housed in a very expensive piece of server hardware (assembled by yours truly), yet give it a few years and a cheap beige box and a motherboard from Asus made toast of the Xeons...

What types of CPUs are you looking at for SMP?

Best regards

Frank N.
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