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It seems that the GPU requires more memory bandwidth than the CPU. Discrete graphics all have dedicated fast memory on board. The integrated GPU shares the same system memory as the CPU.

Would that cause a CPU performance drop when using the integrated GPU?

Because it seems that the integrated GPU might consume quite a lot of system memory bandwidth.

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You should have posted the update as an answer. –  AndrejaKo Apr 10 '11 at 14:58
    
@AndrejaKo: Thanks for the advice. I just tried to post it as an answer, but unfortunately I got an error message saying: "New users can't answer their own question for 24 hours. Please use comments, or edit your question instead." I will try again 24 hours later :) –  user68795 Apr 10 '11 at 15:07
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@caveman It seems that situation keeps getting worse and worse for new users. I never had such problems back when I had low reputation. –  AndrejaKo Apr 10 '11 at 15:12
    
I agree @Andreja. I've posted a comment about this over at Meta.Stack Overflow –  Sathya Apr 11 '11 at 4:44
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While I agree that answer isn't correct, it's still an answer, and I'd imagine that voting would take care of the right/wrong mechanics. @Jeff –  Sathya Apr 11 '11 at 4:57

2 Answers 2

I found 2 related benchmarks. But they were not doing any GPU intensive works while benchmarking CPU performance. In real world, I might be using several GPU and CPU intensive apps at the same time.

1) Tom's Hardware Review: Efficiency Comparison: Sandy Bridge Vs. Intel And AMD CPUs

They were using 2 x 2 GB DDR3-2200, Kingmax FLKE85F-B8KJAA FEIS, which provides much more bandwidth than common DDR3-1333. Regarding CPU performance, it seems for both Intel Sandy Bridge and AMD Phenom II, it made no difference using integrated graphics or discrete graphics.

Benchmark Results: Integrated Graphics Performance: enter image description here enter image description here

Benchmark Results: Discrete Graphics Performance: enter image description here enter image description here

2) This one is quite old, posted 4 years ago: Gigabyte MA69VM-S2 Motherboard on AMD 690V (Socket AM2) Chipset.

enter image description here

The same question were also asked 4 years ago at here.

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integrated GPUs share system memory with the CPU anyway. The advantage of the APU design is lower power consumption, and lower latency in communication between the GPU and CPU.

According to intel, least on their designs this could be up to a 4x performance boost

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But how would that consumption compare to dedicated graphics cards? Also OP never mentioned APUs. –  AndrejaKo Apr 10 '11 at 12:19
    
the GPU/CPU on the same package that sandy bridge uses is a APU. Most APUs seem to be better than previous generation low end discrete graphics, but worse than the high end stuff. –  Journeyman Geek Apr 10 '11 at 13:35
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Thanks for the reply and the links. But I was actually talking about the CPU performance, not GPU/APU performance :) I was wondering if using integrated GPU/APU would cause CPU performance drop. Because it seems integrated GPU/APU would reduce the memory bandwidth of CPU, as the integrated GPU/APU shares the same system memory with CPU, and it seems GPU/APU costs more memory bandwidth than CPU. –  user68795 Apr 10 '11 at 13:52
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sandy bridge uses a VERY different setup from older integrated chipsets - in older setups you were transferring information to from GPU to RAM to CPU. in the APU design, the GPU and CPU can communicate directly. I suppose the only way to really tell is to benchmark, but i don't think those numbers would be accurate for sandy bridge or bulldozer style designs –  Journeyman Geek Apr 11 '11 at 0:07

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