Hello there, welcome to the nvidia forums!
Having been here a little while, I have seen the question "Will these two cards work in SLI?" countless times.
There is obviously quite a bit of confusion out there about the subject - so I will attempt to clarify things.
This is simply a quick guide to what WILL and what WILL NOT work in SLI. For further information regarding the specifics of how SLI works and its benefits, please see the guides at the bottom of this post.
SLI: What works with what?
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 connector(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: GTS450 or better
-- 500 Series: Any
-- Quadro: See HERE
Note: Although some cards in the 6 and 7 series can do SLI, these cards have been omitted due to age.
Note: GPUs with an AGP interface CANNOT use SLI. SLI is only possible on GPUs that use a PCI-e interface.
Note: 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 an Identical model name with identical model name. GTX480 with a GTX480. GTX285 with GTX285. 8800GT with 8800GT. Etc.
The only exceptions to this rule are the 9800GTX, 9800GTX+ and GTS250, which are all technically the same and can work in SLI with each other - assuming the other requirements are met.
(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 GTX275 Co-Op to have SLI GTX275s + GTS250 for PhysX)
Note: The "GT440 OEM" card does support SLI, however it is OEM only - so a system with this kind of setup will come pre-configured. The "GT440 Retail version" is not SLI capable with itself, or the OEM version.
Note: The "GTX460" and "GTX460SE" are not SLI capable with eachother.
- All GPUs must have the same amount of VRAM.
-- You cannot use a '256MB' version with a '512MB' version or '1GB' version with a '2GB' version in SLI. Etc.
Note: It used to be possible to enable SLI on cards with differing VRAM (EG 8800GTS 640 and 320) via the 'coolbits' mod. However, this mod will not work with newer cards or newer drivers.
- An SLI Bridge.
-- Although you don't 'need' to use an SLI bridge with most 2-way SLI setups (it is highly recommend however), you do need to use the correct SLI Bridge for all 3-way, 4-way and Quad SLI configurations.
Note: Using GTX580s in normal 2-way SLI requires the use of an SLI bridge.
- 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)
Note: Using two EVGA GTX275 Co-Ops (or similar multi-GPU cards) 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 to sit idle.
- OEM system exceptions
-- On some OEM systems (Dell / Alienware in particular) you may be unable to SLI the existing Dell OEM graphics card with a standard retail version of the card due to graphics / motherboard BIOS restrictions.
Note: This issue is particularly present with Dell GTX260s and GTX460s.
The following have no effect on your ability to use SLI:
- Manufacturer
-- You can mix and match any manufacturer of nvidia GPUs.
- Clock speeds
-- You are able to use different clock speeds on each GPU working in SLI. An 'overclocked' card will work with a 'plain' card 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.
Note: On very old drivers this feature may be unavailable.
- Number of CUDA Cores (GTX260 only)
-- 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. It is recommend you run the 216 core version as your primary GPU as it will be the fastest.
Note: This does not apply to the GTX460 and GTX460SE - Different model name as well as other engine differences.
- BIOS Version.
-- You can use as many different BIOS versions between the cards you have in SLI as you like.
Other considerations for SLI:
- Motherboard
-- Your motherboard will need to specifically support SLI for SLI to work. Consult your motherboard manual or manufacturer website for this information.
Note: Common motherboards that usually support SLI are the Intel P55, X58 and P67 chipsets. LGA775 and AMD motherboards also support SLI when equipped with an nvidia chipset.
- Power Supply
-- You will need to ensure that your systems power supply is capable of supplying enough wattage and amperage to each graphics card. Power requirements can be found on the nvidia website.
Note: To work out how much wattage you need, look up your graphics card on the nvidia website where you will find the power requirements for a single card. Add the 'Graphics Card Power (W)' figure to the 'Minimum Recommended System Power (W)' figure then overshoot by 100W for safety.
- Case & Airflow
-- Make sure your case is physically big enough to house all the cards you wish to use, as well as being able to provide sufficient airflow.
- CPU
-- To get the most out of SLI, you will often need to overclock the CPU to be able to feed the GPUs. CPU bottlenecking is especially prevalent in high end 2-way, 3-way, Quad and 4-way SLI configurations and may result in low GPU usage.
For a more in-depth look at SLI:
- The Unofficial NVIDIA SLI Technology User Reference Guide
- Nvidia Multi GPU SLI/PhysX Setup Guide.
Last Updated April 11 2011
