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Intel Quad Core or AMD 8 Core for Virtualization

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October 10, 2012 4:07:44 PM

Hello everyone. If comparing a 3.6GHz Core i7 (Quad core, HT) to a 3.9GHz 8-core AMD CPU, which one will perform better with up to 8 VMs? I tried googling and nothing informative really comes up. My guess is that you want more cores and the Intel would bog down, giving AMD a lead here. Thoughts?

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October 10, 2012 4:24:16 PM

Yup you got that right...virtualization handling many VM's is one place where the AMD FX chips really shine bright :) 
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October 10, 2012 5:35:29 PM

k1114, I would agree but HT isn't exactly the same as having another CPU core, especially when you have more VMs than physical cores. The i7 would definitely win running up to 4 VMs, but when you pack 8 VMs on a quad-core, you are sharing one core for every 2 VMs, or an HT thread on every other VM which doesn't sound ideal to me, but perhaps your right.

Anyone else familiar with this?
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October 10, 2012 5:40:34 PM

I'd go with the FX. I've used VMs on Hyper-Threaded CPUs and not even Hyper-Threading makes up the difference of two similarly clocked or higher clocked AMD cores in my experience.

Also, leo2kp, that's not how Hyper-Threading works. Hyper-Threading is two virtual threads sharing a physical core, not one physical thread and one virtual thread.
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October 10, 2012 5:46:17 PM

I'd go with AMD here. Besides the most obvious reason being the price advantage, this is something the FX chip is better at than in other departments.
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October 10, 2012 5:48:35 PM

I see. That's interesting, because when I run a multi-threaded application, it almost always pics threads 0, 2, 4, 6 first (I have a hexacore i7). But on the other hand, when I run Prime95, all threads finish at the same time. It's probably just how Windows handles load balancing maybe.
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October 10, 2012 5:50:57 PM

leo2kp said:
I see. That's interesting, because when I run a multi-threaded application, it almost always pics threads 0, 2, 4, 6 first (I have a hexacore i7). But on the other hand, when I run Prime95, all threads finish at the same time. It's probably just how Windows handles load balancing maybe.


Yeah, that's just optimal scheduling. Windows knows that loading one heavy thread per core and only using Hyper-Threading much when it has no more cores is the best way to schedule threads. Unfortunately for AMD, Windows 7 (even with the hot fixes) has no such scheduling optimization for Bulldozer, one of their larger performance issues with lightly threaded software.
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October 10, 2012 6:25:14 PM

But the bd cores share resources which is one reason why they have less performance. Multi threaded apps is proof enough that even though there are less cores, the i7 has better performance especially since more cores in these apps would be a much better increase than higher clocks. You can see in the link that the 6c at 3.2ghz wins over the 4c at 4.6ghz. If one core with ht is more performance than 2 cores, then in the end the number of cores is irrelevant to end result performance. The fx 8150 is $100 cheaper and for being close to the performance is better bang per buck.
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October 10, 2012 6:35:15 PM

k1114 said:
But the bd cores share resources which is one reason why they have less performance. Multi threaded apps is proof enough that even though there are less cores, the i7 has better performance especially since more cores in these apps would be a much better increase than higher clocks. You can see in the link that the 6c at 3.2ghz wins over the 4c at 4.6ghz. If one core with ht is more performance than 2 cores, then in the end the number of cores is irrelevant to end result performance. The fx 8150 is $100 cheaper and for being close to the performance is better bang per buck.


One Bulldozer module is better than one Hyper-Threaded Sandy/Ivy Bridge core at a slightly lower frequency. Sharing front end resources isn't as bad as sharing execution and front end resources like Hyper-Threading does, although the shared decoders are a problem in of their own.

Also, keep in mind that that this is more than raw throughput. Two cores multi-task better than one core even if they have a slight aggregate performance loss because there is far less switching between running software and better load balancing. A six-core Westmere i7 would be enough to top the FX-8150, but any current quad-core i7 generally loses in virtualization except in highly single-threaded tests. Even when they are similar in performance, there is still a large price difference between i7s and FX-81xx CPUs.
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October 10, 2012 7:58:31 PM

Well thank everyone for your input! My buddy is still going with Intel because he is convinced that his domain controller will have the highest CPU usage, and the rest of his VMs will be largely idle. Personally from a cost/benefit standpoint I would have stuck with AMD, but I couldn't convince him even with your help. :( 
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October 10, 2012 7:59:10 PM

Best answer selected by leo2kp.
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October 10, 2012 8:04:54 PM

That's alright. It's more expensive, but the i7s are still very good CPUs.
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