Hello Philip,
Hauptwerk is fully optimised for multiple CPUs and multiple cores (at least up to 8 cores, since we've never tried it on computers with more cores than .
With all other factors kept constant (clock speed, L2 cache size, bus speed, microarchitecture/revision, etc.), performance doesn't quite scale linearly with number of cores (since there is some overhead in synchronising and load balancing between the cores), but it isn't far off. So given a 4-core CPU and 2-core CPU that were identical in all other regards, the 4-core should outperform the 2-core by slightly less than a factor of two (pehaps 1.8x).
Higher clock rates also give a direct, and usually relatively linear speed increase. E.g. a 2.66 GHz CPU will probably given around 40 percent higher polyphony than a 1.86 GHz CPU with all other factors being the same (number of cores, L2 cache size, bus speed, microarchitecture/revision, etc.).
Looking at Intel's specs for the two processors you mention:
- Intel® Xeon® Processor E5320 (4 cores, 8M L2 cache, 1.86 GHz, 1066 MHz FSB): http://ark.intel.com/Product.aspx?id=28031
- Intel® Xeon® Processor 5150 (2 cores, 4M L2 cache, 2.66 GHz, 1333 MHz FSB): http://ark.intel.com/Product.aspx?id=27218
... the E5320 has four cores compared to the 5150's two, and twice as much L2 cache, but about 30 percent lower clock speed and a slightly lower bus speed than the 5150. I understand that the 5320 is also a later model (microarchitecture) than the 5150, which in itself is likely to give better performance.
So given a choice between just the E5320 and 5150, I would definitely go for the E5320, since I would expect it to give considerably higher performance.
If other models in the E53xx range are an option:
http://ark.intel.com/ProductCollection.aspx?series=30807
... then for future-proofing of those I would probably opt for the E5345:
- Intel® Xeon® Processor E5345 (4-core, 8M L2 cache, 2.33 GHz, 1333 MHz FSB): http://ark.intel.com/Product.aspx?id=28032
... as a good balance between cost and performance. It has a 25 percent higher clock speed (should give approx. 25 higher polyphony) and a faster bus speed for about 42 percent higher price.
However, you might also want to consider some of the more recent processors, e.g. the 54xx series or 55xx series:
http://ark.intel.com/ProductCollection.aspx?series=33905
http://ark.intel.com/ProductCollection.aspx?series=39565
http://en.wikipedia.org/wiki/Intel_Nehalem_(microarchitecture)
E.g. the E5420 (4-core, 12 MB L2 cache, 1333 GHz FSB) seems quite cheap for its spec:
http://www.dabs.com/category/components-and-storage,motherboards-and-processors,processors/11147-50520-40380000
You mentioned in a previous post that you're intending to use the (extremely large) Sonus Paradisi Caen sample set. If you're planning on using the surround version (which uses two voices of polyphony per pipe, i.e. needs about twice the CPU power compared to other comparable sample sets) with large registrations, then you'll need a serious amount of CPU power. From other users of the Caen surround set (I don't have a copy of it myself at the moment, so I can't give accurate benchmarks) 8 cores might even be needed (although of course the non-surround version would be half as demanding, and you can always avoid the largest registrations and thus then get away with less).
If you want something that should give absolutely reliable audio/MIDI performance without compatibility issues, a Mac Pro running OS X might also be something to consider:
http://www.apple.com/uk/macpro/
http://store.apple.com/uk_smb_67752/browse/home/shop_mac/family/mac_pro
(There's no VSTi version of Hauptwerk yet on OS X.)
The Mac Pros use the latest Intel Nehalem Xeon processors.
Hope that helps.