Further information has come to light, while by default Nvidia will only support 2 way SLI configurations, 3 and 4 way configurations are still possible, but “are no longer recommended.” Nvidia have stated this is due to increasing difficulty for 3 and 4 way SLI modes to provide beneficial performance scaling for end users. For instance, many games become bottle necked by the CPU when running in these configurations and games are increasingly using techniques that make it very difficult to extract frame-to-frame parallelism.
With all this said, Nvidia are still allowing for 3-way and 4-way SLI configurations with the GTX1080 via the use of something called an “Enthusiast Key.”
To obtain the Enthusiast Key Nvidia have outlined the following process:
- Run an application locally to generate a signature for your GPU.
- Request an Enthusiast Key from an upcoming Nvidia Enthusiast key website.
- Download your key.
- Install your key to unlock the 3 and 4-way SLI function.
As it turns out, NVIDIA is still being quite coy with the actual details and the representative from EVGA misspoke. In fact, EVGA, and other AIB’s, don’t quite have the information regarding how SLI will work at all. Thus far the HB SLI bridge only comes in one flavor, which spawned the assumption that it would only work with two cards.
Since Nvidia revealed their brand new Pascal architecture featuring their most powerful GPU yet called GTX 1080 there have been some concerns about the new HB SLI bridge they released along side it and how many cards it will actually be able to support. This new HB SLI bridge is supposed to bring about better scaling thanks to higher available bandwidth (HB = High Bandwidth) between the GPUs.
NVIDIA’s new HB SLI bridge design prevents more than two cards from being used
The problem, which some people might have noticed is that on the official Nvidia website, surrounds the fact that there is only one HB SLI bridge and that it only 2 GPUs at a maximum. But because this is just an announcement, me and others thought it is just temporary until they release 3-way and 4-way HB bridge.
Unfortunately it has been confirmed by a member of EVGA tech support that 1080 is limited to 2-way SLI only.
“We can confirm that 1080 cards only support up to 2-way SLI and anything above this will not work, no matter the SLI bridge. Please however keep in mind that if you do use the new SLI bridge along with two 1080 cards, then it gives more performance than 2-way SLI did in the past on previous series.”
This is unfortunate news for GPU enthusiasts that do indeed wish to take advantage of what was supposed to be a resurgence of multi-GPU enabled games. It is especially unfortunate for those who wanted to have the top scores in the 3DMark Hall of Fame.
But on the bright side, this new HB bridge should bring better scaling in games that do make use of SLI. Below you can see the actual connectors themselves that speak to why it likely wouldn’t work to have more than two cards. Each 1080 has 2 SLI connectors but the new HB bridge uses both of them for higher bandwidth, meaning it’s completely incompatible with a third connector, because it simply won’t work.
As for GTX 1070, we’re not sure as the new HB bridge is only compatible with the GTX 1080, so this shouldn’t affect the GTX 1070 at all. And for future more powerful Pascal GPUs? It might be possible for NVIDIA to take advantage of their new connector with up to 4-way configurations, though a connector for that has yet to be revealed. Despite it not necessarily being the best decisions and not always providing the boost in performance we expect, 3-way and 4-way SLI can be quite fun for the PC enthusiasts out there.