RE: SLI And Having 2 or more Graphics Cards

Hi all,

Can somebody explain to me the basics and advanced solutions and generics behind SLI and dual graphics cards on a motherboard please.

Reason being is that a client specifically wants a motherboard with 3 PCI express slots and wants three graphics cards on this, and I have another order to equip a machine with 2 graphics cards again on one motherboard.

have looked around and there is no decent guide on SLI or the features and specifics on this at all.

Can somebody help me on this.

Cheers all

Kai

When researching my new system, I found that the PCIe speeds differ for each slot. Check your mobo's specs to make sure the video cards minimum speed will be supported on each slot. Most have one slot thats 16x, one thats 8x and one thats 4x. Also will they be running the cards independantly or witht he use of two cards are they wanting to run Crossfire mode?

Hi,

Theyll be running in Crossfire mode to give maximum speed capabilities. So I am right in saying that theyll have to buy 1 16x, 1 8x and 14x if they indeed wat to run 2 or more graphics card theyll ned to bu the appropriate speed cards in accordance to the slot speeds that are allocated? or in xfire mode does this not apply.

Also, this is a stupid question. If there is one monitor processing the signal, I take it that in order to work properly, there is only one monitor needed? :-)

And, if there is a monitor inserted into each card, does it process the same signal, or does it act as a dual monitor card?

Thansk alot

Kai

If they are running in Crossfire mode then they will be running in parallel for the two cards with a single output. Its basically a gamer config and if they are looking to use this system as some kind of multimonitor business system then it wouldnt help them to run it in crossfire then.

When cards are run in crossfire they will reduce their speeds to 8x on each card. So since they will be dependant upon the mobo support and video cards and what ever they are going to apply it to will matter.

I have 2 dual video cards in my system and onejust runs at a slower bus speed. Since I am not a gamer its ok. My video cards run at 16x but also support 8x so I am good there. I can have up to 4 monitors hooked up all independant or other configs. If I was to place them into crossfire mode then I would get a single monitor output.

Just read that only one monitor is needed so then crossfire could be useful but only 2 video cards could be used. What is their plan for the system with 3 cards to be in it?

Hi,

The three card configuration is just an option at the moment.

So basically, if you have two cards both running at 16x, theyll be supported by the motherboard at 8x, use the appropriate capabilities of each card put together, o is there a specific supported speed in accordance of the motherboard specifications and support that theyll run at?

And, if this system has one monitor (and it is a gaming system) is there any specific one it should be plugged into? (IE the 16x slot)

Another one is what are the advantages of SLI compared to one graphics accellerator with massive memory such as a GeForce titanium 7800 or something to this effect, compared to running two accellerators in parrallel with the slower speed specifications.

Thanks indeed

Kai

This is a little out of my range when it comes to gamer systems but I understand that for my mobo one slot at 16x and another at 8x so when in crossfire mode they both run at 8x for the higher performance of running in parallel. My third pcie port is at 4x but specifications didnt say if it could support a videocard. Seems like just about all the pcie videocards I evaled were at 16x.

Quote:

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•Two PCI Conventional bus add-in card connectors (SMBus routed to both PCI Conventional bus add-in card connectors)
• One Primary PCI Express* x16 (electrical x16 or x8) bus add-in card connector
• One Secondary PCI Express* x16 (electrical x8) bus add-in card connector
• One PCI Express* x16 (electrical x4) bus add-in card connector

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http://www.intel.com/products/mother...5xbx/index.htm
Some good stuff on the Intel link for my mobo.


Crossfire:
http://ati.amd.com/technology/crossfire/index.html


Also, make sure your PSU can handle the extra wattage useage by the PCIe cards and supports SLI.

Here is my new system with the 2 ATI dual DVI outputs per card. It supports 4 monitors using only two cards as this may be a cheaper option then getting a third videocard. :)

6" cooling fans look small but they are powerfull with high CFM's.

Hi,

So in a nutshell.

Graphics cards running in parrallel run at 8x and use all available resources available on both graphics cards native to this speed. (I.E 2x 512MB @ DDR3, 2x bus speeds @400mhz, etc)

Running two graphics cards at the same speed is recommended and is generally better that one card as there are more resources available.

the third slot is a bag of poo.

Anything ive missed?

Many thanks indeed

Kai

Nope, I think that is it in a nutshell. The crossfire mode really takes advantage of each cards dual monitor resources channeled as a single output. Then with each card doing this you end up with two single outputs joined by a special "Y" adapter video cable which supercharges the output as a single output video signal. Completely a gamers video mode of choice.

Hang on.

So to take full advantage of this output, youll need to connect both outputs to a monitor with a reverse split cable ( Y join cable).

Sorry to sound stupid, but gaming is also not my thing at all.

Cheers Rob

Kai

Yes, I can dig up my boxes for my cards but I believe the cable comes with the card. The cable "Joins" the two outputs to a single output for your single monitor.

Quote:

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Originally Posted by RobDog888

Yes, I can dig up my boxes for my cards but I believe the cable comes with the card. The cable "Joins" the two outputs to a single output for your single monitor.

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Each card either renders half the screen, or one frame at a time, so, you'd end up with 2 frames being rendered giving each card an extra frame to breath, or, pre-render the next frame :)

There are also criss-cross modes where quarters or less of the screen are rendered each (for example each card takes a quarter of the sky, and something that's easier to render)

There is about 4 modes of rendering that you can configure too with crossfire.