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Phenom 9500 on AM2 rather than AM2+, any noticeable decrease in perfor

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March 1, 2008 12:23:32 PM

Hi,
I'm limited to buying a AM2 motherboard rather than AM2+ for the Phenom 9500.
The motherboard I'm thinking to buy is the Asus M2A-VM. It is listed in AMD site as being
compatible for the Phenom 9500.

I know the difference between AM2 and AM2+ is in two things:

* HyperTransport 3.0 operating at up to 2.6 GHz
* Split power planes: one for the CPU cores, and the other for the Integrated Memory controller (IMC). This will improve power savings, especially with integrated graphics, if the CPU cores are in sleep mode but the IMC is still active.

http://en.wikipedia.org/wiki/AM2%2B

The question now is, is there a noticeable decrease in performance when using Phenom CPUs on AM2 motherboards?

Is there any sites that did benchmarks on this?
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March 1, 2008 1:04:08 PM

I have 3 of these mobos but decided to leave the X2 cpus in them.

I have the same concerns ... and decided to leave it at that.

I would imagine the answer to your question is probably yes ... but I don't know for sure.

I wouldn't stick a new quad core cpu in a cheap mobo ... seems just rude.

Plus for my kids who game I could not warrant the expense going up to the quad core when most of their games are barely dual core optimised anyway.

cheers !
March 1, 2008 1:39:06 PM

A very interesting question.

While i don't know the results for sure, i would suggest to stick to x2 processors on am2 boards unless you really need more cores for video rendering or similar multi-processor intensive tasks.
The slower hypertransport will reduce performance and if the TLB patch is in place, performance will suffer even more. While i don't know it, i suspect that single threaded performance of a Phenom compared to an x2 will be about equal if not worse under some circumstances.
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March 2, 2008 2:16:40 AM

I'm one of those that still thinks that old HT has a lot of room that hasn't been limiting performance. Just like PCIe 1.1 vs PCIe 2.0 but in this case the performance impact exists, and is noticeable by 2 or 3%.

My theory is that actual phenoms won't suffer a lot of bottleneck on old HT, but future phenoms may suffer, as they'll become faster and faster.

If my theory is true or false I don't know, we have to proove it.
March 2, 2008 5:29:31 AM

Yes you will see decreased performance as the AM2 MB does not support any of the features that allow the Phenom to pass the older chips ratings.
March 2, 2008 6:06:22 AM

A definit no.
Obviously the split planes will do zip for perf.
People here have been running tests on HTT since it first came out.
Single core chips have been shown to run without loss, at just above 200 mhz. Dual cores would be fine ~ 500mhz, so quads will have no problem @ 1ghz or more. Remember, the HTT bus is not used for memory, so it requires a lot less bandwidth than the old fsb.
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