Video card crossfire and sli compatibility sticky?

[Rakuma]

So during my short time here I have noticed that a common question is "What card can I get to crossfire/sli with X" I've done some research and pulled up relevant information and was wondering if we could sticky it in an appropriate forum?

This is good reference to SLI.

SLI: What works with what?

Needing 'Identical' cards isn't exactly 100% true.

In order to run two or more nvidia GPUs in SLI, you need the following:

-Two or more SLI capable GPUs
(These are easily spotted by the SLI connection(s) on the top of the card, where the SLI bridge connects.)
-- 8 Series: 8500GT or better
-- 9 Series: 9500GT or better
-- 200 Series: GTS250 or better
-- 300 Series: These are OEM only cards. Whether SLI is possible or not depends on the manufacturer of your specific system.
-- 400 Series: Any (currently)
-- Quadro: See HERE
Note 1: Although some cards in the 6 and 7 series can do SLI, these cards have been omitted due to age.
Note 2: GPUs with an AGP interface CANNOT use SLI. SLI is only possible on GPUs that use a PCI-e interface.
Note 3: Support for SLI may be unavailable on older cards (6 series, 7 series, lower 8 series) with newer driver sets.

- All GPUs must have an identical model name.
(This means the simplified model name for the base GPU as it appears on the nvidia website. An EVGA GTX480 Hydro Copper FTW Edition is simply a GTX480 in terms of SLI.)
-- You can only SLI together a GTX480 with a GTX480, GTX285 with GTX285 etc. Identical model name with identical model name. The only exception to this rule is the 9800GTX, 9800GTX+ and GTS250, which are all technically the same hardware and can work in SLI with each other.
(A good example of this principal is the EVGA GTX275 Co-Op. This card uses two different GPUs (a GTX275 and a GTS250) on one board. You can use a normal GTX275 in SLI with the Co-Op to have SLI GTX275s + GTS250 for PhysX)

- All GPUs must have the same amount of VRAM.
-- You cannot use a 'GTX285 2GB' with a 'GTX285 1GB' (or similar) in SLI.

- An SLI Bridge.
-- Although you don't 'need' (it is highly recommend however) to use an SLI bridge with a traditional 2 card SLI setup, you do need to use the SLI Bridge for 3-way, 4-way and Quad SLI.

- Only one type of SLI'd card per system.
-- You cannot have 2 different pairs of cards in SLI in the same system. (EG 2x GTX285s + 2x 9800GTXs)
(Using two EVGA GTX275 Co-Ops (or similar) falls under this category. The GTS250s will be unable to be used in SLI in tandem to the two GTX275s. One of the GTS250s will be forced sit idle.)

The following do NOT effect your ability to use SLI.

- Brand
-- You can mix and match any two (or more) brands of nvidia GPUs.

- Clock speeds
-- You are able to use different clock speeds on each GPU working in SLI. A 'super-clocked' card will work with the 'plain' version just fine. For best performance, it is recommend that you run both cards at the same clocks or use the faster card as the primary GPU.

- Number of CUDA Cores
-- This applies to the GTX260 which has 2 versions. One has 216 cores, the other has 192. They are able to work in SLI as they meet the requirements above. As in the above example, It is recommend you run the 216 core version as your primary GPU.


For a more in-depth look at SLI:

- The Unofficial NVIDIA SLI Technology User Reference Guide

- Nvidia Multi GPU SLI/PhysX Setup Guide.

And ATI's is really simple!

What do you think? Good idea? Did I miss it somewhere? And also I'm more than happy to keep up to date with new generations and the like.

 

[foothead]

The only exception to this rule is the 9800GTX, 9800GTX+ and GTS250, which are all technically the same hardware and can work in SLI with each other.

You missed G92-9600 GSO + 8800 GS, as well as all hybrid SLI configurations (see here) Also, 9800 GTX is NOT the same hardware as 9800 GTX+ or GTS 250. The 9800 GTX's G92 is manufactured on a 65nm process, while the GTX+/GTS 250 is 55nm. There are also differences in PCB layout and clock speeds, as well as power consumption, due to reduction in die size.

-Two or more SLI capable GPUs
(These are easily spotted by the SLI connection(s) on the top of the card, where the SLI bridge connects.)

Not necessarily. Any card with the SLI bridge connector will support SLI, but is not always on the top. I've seen a couple custom PCB cards with it on the end of the card, as well as very old cards, where it was on the backside of the pcb. Alslo, soft SLI has been shown to work on some cards that have no SLI connector at all, and any hybrid SLI configuration will not have it.

All GPUs must have the same amount of VRAM.

Incorrect. Coolbits (which has been included in NV drivers for some time now) allows you to do this. It should enable by default, and it will basically force both cards to use the VRAM of the lower card. So if you had two cards at 512MB and 1GB, only 512MB would actually be used on each.

GPUs with an AGP interface CANNOT use SLI. SLI is only possible on GPUs that use a PCI-e interface.

SLI has been around since 3Dfx days. IIRC, the voodoo2 was the first to offer the feature. So, no it is available on non-PCI express cards. Also, it seems that SLI does work with NV AGP cards (see here), including configurations with PCI express and AGP.

9 Series: 9500GT or better

- Clock speeds
-- You are able to use different clock speeds on each GPU working in SLI. A 'super-clocked' card will work with the 'plain' version just fine. For best performance, it is recommend that you run both cards at the same clocks or use the faster card as the primary GPU.

This is backwards. The lower clocked card should be run as the primary, so the higher clocked card will match it. If not, you will likely run into lots of issues.

All GPUs must have an identical model name.

This does not necessarily mean they are compatible though, even if the two are SLI capable. For example, there are two 9600 GSOs, one being 192-bit G92, and the other is 256-bit G94. I've also seen a couple 32SP 9400 GS'es floating around, which are not compatible with the typical 16SP 9400 GS.

Number of CUDA Cores

See above.

-- Although you don't 'need' (it is highly recommend however) to use an SLI bridge with a traditional 2 card SLI setup, you do need to use the SLI Bridge for 3-way, 4-way and Quad SLI.

I would consider it necessary to use a bridge if at all possible. Without it, the soft SLI can (and will unless the cards are POS) use so much CPU/chipset use that it will create massive bottlenecks, most likely causing a drop in performance from even a single card.

-- 200 Series: GTS250 or better

GTS 240 has a SLI bridge. (see image here)

CrossfireX chart is also horribly incomplete.

Missing cards (not a comprehensive list):

HD 5670: Compatible with HD 5670
HD 5570: compatible with HD 5570, HD 5550
HD 5550: Compatible with HD 5550, HD 5570
HD 5450: compatible with HD 5450
HD 3830/3690: compatible with HD 3830/3690, HD 3850, HD 3870, HD 3870 x2
HD 2900: compatible with HD 2900
HD 2600: compatible with HD 2600, HD 2600 x2
HD 2600 x2: compatible with HD 2600 x2, HD 2600
HD 2400: compatible with: HD 2400

Anything older than this, I won't bother to list. I find it rather odd that they included some of the 5000 and 3000 series but not others.

These are just the errors I caught while reading this, so I am sure there are more. Might I ask what your sources are?

BTW, yes I am being nitpicky, but I prefer informational threads to be 100% accurate.

 

[coyahud]

Computer TIPS AND TRICK