# What type of motherboard



## twilyth (Dec 11, 2014)

This is pure speculation at the moment but I've been searching fleabay for v3 Xeon chips and the prices seem to be coming down nicely.  It looks like 14 core chips are already getting close to the $700-800 mark so maybe in another 3-6 months I'll consider buying components for another system.

My question is, if I decide to do that, should I go for a m/b that has 1 or 3 PCI 3 x16 slots?  I have no need for these unless we get another gpu project.  But if that happens, I would probably get something like an R295x2 which IIRC has around 12k shaders.

From the last project, I remember that 2 7970's with around 2k shaders each was able to keep the 32 thread machine pretty busy.  So I'm thinking that one 295x2 should be able to provide work for 56 threads pretty easily.  But I don't know.  Opinions?


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## [Ion] (Dec 11, 2014)

Well, my experience was that a single i7 was more than enough for a single HD7950 (an OCed Sandy chip for a stock HD7950).  Even with an i3 it did about 90-95% of the performance of the i7 chip (IIRC running something like 10 WUs at once since it does't take a full thread to run a GPU WU) So, IMO, you're probably underestimating the number of GPUs that you could run.

That being said, planning around a future unknown project seems challenging and perhaps unwise.  Just my 2c though.


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## twilyth (Dec 11, 2014)

A 3 PCI 3 x16 board would give me more flexibility I guess.  It's just that these are all e-atx boards which means I'd probably use the bench setup instead of a case.  The old SR-X board is occupying that now so I'd have to get rid of that but I guess that's no great loss seeing as I would only have one old 5645 chip to put in there.  Everything else is ready to go including the 1200 watt psu.  So I would just need the m/b and maybe some new memory sticks since I think everything I have now uses DDR3.


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## [Ion] (Dec 12, 2014)

Sounds like quite an amazing setup!
These are the Haswell CPUs you're looking at, right?


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## twilyth (Dec 12, 2014)

Right.  Mostly ES.  There are lots of new chips but at retail prices that are 2-3x the cost.


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## [Ion] (Dec 12, 2014)

twilyth said:


> Right.  Mostly ES.  There are lots of new chips but at retail prices that are 2-3x the cost.


ES CPUs are often quite cheap for the performance you get--the X5670 has done well and I have high hopes for the X5650 too.


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## t_ski (Dec 13, 2014)

IIRC, I was running 24 threads on a 3930K and three 7970's, but I could be wrong.  It was so long ago


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