AFAIK, the max available PCIe slots on mobo for 4 double slot GPUs is 4.
You must have enough space between the slots for to insert a double slot GPU.

The upper mentioned MSI mobo is the cheapest around.
IIRC, now the 3rd version available.

Also if your mobo have 7 PCIe slots, if you connect all slots - the speed go down.
In past the mobo chips could manage max. 32 PCIe lines.
For my mobo this mean.. 32 / 4 = 8 .
4x PCIe 2.0 x8 .
If my mobo would have only PCIe 1.0 and x8, I would see performance loss.

The new mobo chips can manage more lines.


Yes, I had good luck and have a CHIEFTEC PC case.
Only 7 slot openings, but enough space to the bottom for the 4th double slot GPU.
So I took my DREMEL and cutted a 8th opening into the PC case.

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AFAIK, for max. CUDA performane PCIe 1.0 x16 or PCIe 2.0 x8 (electric) slot for every GPU.

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[...]
A x58 motherboard I was looking at was designed to run 4 slots @ PCIe x8 or 2 slots @ PCIe x8 mode. Motherboards like P6T6 WS Revolution let you run 3 slots @ PCIe x16 mode.

Ohh.. this are Intel mobos, right?

Then I must make advertisement for AMD..

In the time (for around one year) I was looking for a mobo which have 4x PCIe x16 slots, I found only one mobo.. MSI K9A2 Platinum.
If two GPUs.. you have 2x PCIe 2.0 x16 (electric). If four GPUs (like I have) you have 4x PCIe 2.0 x8 (electric).
So very well for CUDA crunching.

How about this one, Asus P6T7 WS Supercomputer
7 PCI-E Gen2 x16
No matter what your preference is, seven PCI-E Gen2 x16 Slots gives you the sufficient I/O interfaces to fulfill your demand for graphic or computing solution. You’ll be able to run both multi-GPU setups. The board features SLI on demand technology, not only supporting up to three graphics cards in a 3 way SLI but also supporting up to four double-deck GPU Graphics cards. Whichever path you take, you can be assured of jaw-dropping graphics at a level previously unseen.

P6T7
Sure wish someone would buy this for me...

The P6T7 is a great board, meant for mainstream computing. AFAIK you can only populate 4 of the 7 PCI-E 2 slots at a time. Regardless, only 4 double volume GPUs will fit in it. It is also expensive. I have the newer version of the MSI K9A2 Platinum, called the MSI 790FX-GD70. It is on an AMD platform, which is far cheaper than the Intel ones. The current drawback is obviously the AMD CPU that goes with it, but if you are getting a GPU cruncher, this will not be much of an issue. AMD CPUs drive GPUs as well as or even better than the Intel CPUs. Also, I bought myself a cheap AM3 CPU while I wait for the new AMD CPUs to be launced in Jan/Feb. The gap to the Intel CPUs will close, but the question is by how far and for how long. I have also seen motherboards with 7 double volume GPU slots. These are aimed at the commercial market and VERY expensive. From what I gather, the S@H apps/BOINC will "only" recognise 8 GPUs anyway, so that would not be too usefull right now anyway. As an aside, anyone buying MSI motherboards better know their stuff if they wish to upgrade their BIOS. I took me 3 weeks to recover from my attempt, and I got very lucky in the end.

[...]
As an aside, anyone buying MSI motherboards better know their stuff if they wish to upgrade their BIOS. I took me 3 weeks to recover from my attempt, and I got very lucky in the end.

No prob here..
I made an online Windows BIOS update with my MSI K9A2 Platinum and after some seconds DL & reboot everything fine.

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[...]
As an aside, anyone buying MSI motherboards better know their stuff if they wish to upgrade their BIOS. I took me 3 weeks to recover from my attempt, and I got very lucky in the end.

No prob here..
I made an online Windows BIOS update with my MSI K9A2 Platinum and after some seconds DL & reboot everything fine.

The online Windows BIOS update may work better than M-Flash, but looking at the problems on the MSI forums I doubt it. I managed to extract my "corrupt" BIOS before I flashed an uncorrupted one. It turns out that M-Flash does not understand fragmented files, so when I initially flashed the BIOS image, M-Flash counted 1MB of data from the starting point of the file. Unfortunately for me, the BIOS image on the flash drive was not contiguous, resulting in part of MS Word documents, images, XML files etc getting flashed onto the BIOS chip. It even overwrote the BIOS boot block, making recovery through the BIOS impossible. If you are interested, this was the only way to recover: http://forum-en.msi.com/index.php?topic=133578.0

[...]
[IMG] http://i110.photobucket.com/albums/n86/hiamps/new-computer1.jpg [/IMG]_switched off

Because of the other thread about case closed/opened.

If you let run CPU water cooling the mobo chip will be not cooled like it from a top flow or the stock heatsink will be done. They are designed for this.

I have a top flow heatsink in my GPU cruncher. Mobo chip and system RAM is cooled also.

A tower heatsink in my QX6700, so the area around the CPU isn't cooled. So I have two small fans (40mm) added to the stock heatsink from the mobo chip.
[EDIT: The system RAM is also cooled with two fans (IIRC, 50mm), because of OC.]

I can't measure the chipset temps with both mobos, so I can't say if it really help.

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BTW.

I don't know how to install this radiator.

Maybe it would be better to turn him 180° ?
That the connectors are on the bottom?

It depend how the water circulate.

It's written in the manual?

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I think not having a CPU fan is what makes my MB temps high. The waterblock stops air flow to the chipsets around the CPU. I need to find the Bracket for the fan to fit on the chipset. Even with the house fan if it isn't turned just at the right angle the temps will go up 7-8 C. My computer creates 450 watts of heat, that is like a small heater. In my case I would just be sucking warm air across everything with case closed as air heats up quick. All my other machines will run within spec temps with covers on but they run cooler without and I tested them all. Heat kills electronics so within spec or not I want mine as cool as they will run. Curious why the MB temps go so much higher with HT off? HT off MB is at 45C and if I turn HT back on it will drop to 37C, and the cover would work.

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Official Abuser of Boinc Buttons...
And no good credit hound!

BTW.

I don't know how to install this radiator.

Maybe it would be better to turn him 180° ?
That the connectors are on the bottom?

It depend how the water circulate.

It's written in the manual?

I need to take a new picture, I have since moved it out of the case with just a little help from my drill. It is now mounted to the cross member that the PS sits on, so in this machine the door is history.

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Official Abuser of Boinc Buttons...
And no good credit hound!

[...]
Curious why the MB temps go so much higher with HT off? HT off MB is at 45C and if I turn HT back on it will drop to 37C, and the cover would work.

I don't know really, but I guess..

If you have HT on, you have less GHz @ the CPU.
If you have HT off, you have more GHz @ the CPU.

So the higher GHz (transfer of data) make the mobo chip (northbridge) hotter.


I guess I'm with the explanation wrong, but with the result right..

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[...]
Curious why the MB temps go so much higher with HT off? HT off MB is at 45C and if I turn HT back on it will drop to 37C, and the cover would work.

I don't know really, but I guess..

If you have HT on, you have less GHz @ the CPU.
If you have HT off, you have more GHz @ the CPU.

So the higher GHz (transfer of data) make the mobo chip (northbridge) hotter.


I guess I'm with the explanation wrong, but with the result right..

Moved my fan for a second and now MB is 49C and CPU is 52C.

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Official Abuser of Boinc Buttons...
And no good credit hound!

Got it up to 4.0 Mhz for an hour before it restarted on its own. Was able to run the performance test from the other thread and seti and CPU temp only got to 62C, I think I may just need a bit more voltage now. On the restart didn't get the overclock fail message and it seemed like it was going to start right back up. I stopped it and set it at 3.8 and it is humming along great. After more than an hour my CPU is 52C and Motherboard is 47C. Don't think temps are stopping me.

Four Megahertz? That's more than twice as fast as my Apple ][.

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[...]
Curious why the MB temps go so much higher with HT off? HT off MB is at 45C and if I turn HT back on it will drop to 37C, and the cover would work.

I don't know really, but I guess..

If you have HT on, you have less GHz @ the CPU.
If you have HT off, you have more GHz @ the CPU.

So the higher GHz (transfer of data) make the mobo chip (northbridge) hotter.


I guess I'm with the explanation wrong, but with the result right..

Ah, actually, you have the same clock rate (number of GHz) spread across more threads, so it should be about the same.

I can accept that it'd be different, but I can't figure out why.

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