AMD FX 8-core or 6-core?

GTCo8 · January 6, 2012, 14:51

Quote:

Originally Posted by Jordi

what's wrong with AMD?

Nothing is wrong.

I see that AMD FX 8150 (8 cores, Bulldozer) in some activities is comparable in speed to Intel i7-2600 (4 cores, Sandy Bridge) and it is only little cheaper than Intel. But only in some. Core per core is worse than Intel. Maybe this will change a little in improved Windows 8 and new Linux kernel. I have read that FX 8100 will be optimal (price vs speed).

Another problem with AMD MOBOs is that they support less memory (usually 4 banks, Intel have 6 or even 12 banks). I mean desktop MOBOs, not Server MOBOs.

And one thing more: MOBOs for AMD are cheaper than for Intel.

wyldckat · February 1, 2012, 06:35

Greetings to all!

Just to give a small update on this subject:

scipy posted some more numbers a while back: Which is better for CFD 4 core i7-2600 or AMD 8 core FX-8150?
I picked up on this report: http://www.phoronix.com/scan.php?pag...r1_ofast&num=1 - this clearly indicates that not using the right options for compiling for the AMD Bulldozer, will affect the runtimes everyone is getting!

So, when in doubt, contact your CFD software supplier and ask them if and which versions of your favourite solver/meshers have been tuned for the AMD Bulldozer or any other CPU architectures!

Best regards,
Bruno

daveatstyacht · February 3, 2012, 16:59

Scipy,
Thank you for going and benchmarking the two systems, I had not considered AMD as a possible candidate for my next CPU. The fact that overclocking the intel did not help your performance says to me that a different part of your system is bottlenecking the performance (probably the bus or memory). Interestingly, I went into researching the differences that might give the FX 8150 an edge and an area that it beats the 2700k is L2 cache hands down (2048 KB per two cores vs 256 KB per core or in other words 8 times more!). Since cache misses can have a huge effect on performance, the larger L2 cache could help significantly, particularly if something like multi-grid is being utilized. Another thing to consider is the maximum supported memory speed 2700k: 1333 MHz vs the 1866 MHz of the FX 8150. Memory speed is an important consideration for unstructured meshes. I think Bruno brings up an excellent point considering the potential bias that can be introduced by the compiler.

Dave

Sources:
Comparison of the two:

http://www.knowbytes.com/home/articl...us-amd-fx-8150

And to confirm the numbers are all correct go to the product pages:

http://www.amd.com/us/products/deskt...omparison.aspx
http://ark.intel.com/products/61275/...che-3_5-GHz%29

rmh26 · February 7, 2012, 09:25

The L2 and L3 cache's are shared on Intel's processors (smart cache) so a four core i7 would be able to share 1Mb of L2 and 8Mb of L3 while a FX4100 would have two independent 2Mb L2 caches(one per FPU unit) and a shared 8Mb L3. The completely shared cache would seem to give Intel an edge for smaller threaded problems while AMD would win out when working on larger sets.

I would say a big plus on AMD's side is the inclusion of FMA which would greatly speed up many linear algebra operations. I don't think Intel will get FMA until Haswell.

February 1, 2012, 06:35		#22
wyldckat Senior Member Bruno Santos Join Date: Mar 2009 Location: Lisbon, Portugal Posts: 2,193 Blog Entries: 30 Rep Power: 24	Greetings to all! Just to give a small update on this subject: scipy posted some more numbers a while back: Which is better for CFD 4 core i7-2600 or AMD 8 core FX-8150? I picked up on this report: http://www.phoronix.com/scan.php?pag...r1_ofast&num=1 - this clearly indicates that not using the right options for compiling for the AMD Bulldozer, will affect the runtimes everyone is getting! So, when in doubt, contact your CFD software supplier and ask them if and which versions of your favourite solver/meshers have been tuned for the AMD Bulldozer or any other CPU architectures! Best regards, Bruno __________________ List of threads useful for building OpenFOAM and other Third Party tools

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February 3, 2012, 16:59		#23
daveatstyacht Member Dave Gross Join Date: Jul 2010 Posts: 90 Rep Power: 3	Scipy, Thank you for going and benchmarking the two systems, I had not considered AMD as a possible candidate for my next CPU. The fact that overclocking the intel did not help your performance says to me that a different part of your system is bottlenecking the performance (probably the bus or memory). Interestingly, I went into researching the differences that might give the FX 8150 an edge and an area that it beats the 2700k is L2 cache hands down (2048 KB per two cores vs 256 KB per core or in other words 8 times more!). Since cache misses can have a huge effect on performance, the larger L2 cache could help significantly, particularly if something like multi-grid is being utilized. Another thing to consider is the maximum supported memory speed 2700k: 1333 MHz vs the 1866 MHz of the FX 8150. Memory speed is an important consideration for unstructured meshes. I think Bruno brings up an excellent point considering the potential bias that can be introduced by the compiler. Dave Sources: Comparison of the two: http://www.knowbytes.com/home/articl...us-amd-fx-8150 And to confirm the numbers are all correct go to the product pages: http://www.amd.com/us/products/deskt...omparison.aspx http://ark.intel.com/products/61275/...che-3_5-GHz%29

February 7, 2012, 09:25		#24
rmh26 Member Join Date: Jul 2011 Posts: 30 Rep Power: 2	The L2 and L3 cache's are shared on Intel's processors (smart cache) so a four core i7 would be able to share 1Mb of L2 and 8Mb of L3 while a FX4100 would have two independent 2Mb L2 caches(one per FPU unit) and a shared 8Mb L3. The completely shared cache would seem to give Intel an edge for smaller threaded problems while AMD would win out when working on larger sets. I would say a big plus on AMD's side is the inclusion of FMA which would greatly speed up many linear algebra operations. I don't think Intel will get FMA until Haswell.