Building an evolutive workstation

[Sam]

Hey guys,
Im currently looking at which pieces im gonna put in my next workstation.
I already builded workstations at work but never mutli-gpu ones

I want advice for a workstation with one gtx260 (or gtx275) that can evolve in a triple gtx260 (or gtx275) setup later
So I need a power supply that can take three gtx260 without problems, a motherboard with three pci-e
And enough memory for all the GPUs. For CPU I will use an i7, don't know wich one yet.

For power supply I looked at Enermax ones
REVOLUTION85+ 950W CrossFireX
REVOLUTION85+ 950W SLI
I don't know why there's two different models, because beside the name I didn't find any features difference

I need to find a good motherboard that can run three gtx260 at full speed without SLI
Anyone got a multi-gpu setup and can share wich motherboard he use?

Here's the motherboard I found
Asus intel socket 1336 P6T
It says 3 x PCIe 2.0 x16 (at x16/x16/x4 mode) what x16/x16/x4 mode mean ?

At first I will buy my workstation with only one gtx260 and I will wait for Octane to support multi-gpu
Also does multi-gpu work better inside windows if they all got the same ammount of memory?
For example if you have three gtx260 you should have six 2gb dimm? So each gpu got 4gb memory

I also need to know if with three gtx260 Octane render will not slow down all the windows UI
Or do I need to find a four pci-e motherboard an add a cheap GPU only for windows

(edit: damn im sorry im in the wrong forum, should be on OS, Drivers & Hardware )

[pixelrush]

I'm looking for a few of those answers myself.
You will need to find a power supply with 8 x 6/8pin connectors for 3(+1) video cards. I think the one you have linked here has 4x = 2 cards
This will probably mean the bigger W supplies.
Have a look at this Nvidia sli page http://www.slizone.com/object/slizone_build_psu.html
I think you will want to run a few exta fans too if it is going to be force fed pixels.

re the pci-e from wikipedia

A PCIe card will fit into a slot of its physical size or bigger, but may not fit into a smaller PCIe slot. Some slots use open-ended sockets to permit physically longer cards and will negotiate the best available electrical connection. The number of lanes actually connected to a slot may also be less than the number supported by the physical slot size. An example is a x8 slot that actually only runs at ×1; these slots will allow any ×1, ×2, ×4 or ×8 card to be used, though only running at the ×1 speed. This type of socket is described as a ×8 (×1 mode) slot, meaning it physically accepts up to ×8 cards but only runs at ×1 speed.

[Sam]

Ok so to run at full speed I need to find a motherboard running at (x16/x16/x16) mode ?
The enermax in 1050W config support three cards, thanks for the slizone link lot of good info there.

Gtx260 needs two 6/8 pin connectors ? That's freakin insane

For extra fans, I already got ideas and brands

[candide]

Why stop at 3 cards? http://fastra2.ua.ac.be/

[pixelrush]

@ candide,
Thats an interesting link.
They have some trouble with stability I read.
I think their pci-e extensions perhaps but also heat.
You see the IR video? one hot box there..60 deg C inside everywhere = like scalding hot water , and this is not the actual chips temp...
Too many cards close together. also draws 2800W power
I know they have a use for high speed calcs but I think they go too far with eyes like this
They should wait for fermi cards and use less IMO.

@sam
There are some cards that have slots where as you add cards they share bandwidth. I looked at Gigabyte and this seems to be the case for all theirs.
They fall back to 8x for 3 cards. This might be quite ok though cos stuff isnt being passed between cards and only some to the cpu for Octane.
4x might be something to skip over.
Asus has one which is 3x 16 http://www.asus.co.nz/product.aspx?P_ID ... templete=2
This is probably pretty expensive card though and possibly overkill.
I'd suggest you look around for a mobo that runs as 8x for 3 cards and keep in mind these graphics cards are double slot wide.

EDIT: I found some info that a practical measured max transfer between cpu and gpu is about 6gb/s so I guess 8x is fine but if you can find a 3 slot x 16 you are covering it better.