3-way SLI question

[biuro74]

Hi,

I'm wondering if some of you guys who have 3-way SLI tried to use them with no SLI bridge (and if it worked, of course). That's question nr 1.

If answer if yes-yes so my second question is still valid. I'm happy 790i-based mobo user and I've got 2 SLI cards. But they are "normal" SLI cards, just with one SLI slot each. I've tried to get rid of my SLI bridge and everything was quite fine, no efficiency drop. Cards are x16 2.0, working as x16 2.0 both. Resolution is 1680x1050 and my cards can do AA maximum x4, so maybe it's a reason why cards don't need that bridge indeed - simply there's no need to transport huge amount of data and PCIe lanes can handle it as is.

But last time I borrowed third card (almost the same, core is exactly the same) from my son to some experiment. I wanted to see if they worked together in 3-way SLI with no bridge. The answer was - no. System (WindowsXP) detected SLI and informed me that there was no bridge, and SLI is still available but at lower speed. OK, I thought. But when I checked GPU-Z it said SLI is enabled, but just 2-way SLI. So Windows treated "slower SLI" as 2-way SLI. Next I've tried to join card like this:

Slot 1 - PCIe x16 2.0 - My Card Nr 1 *** BRIDGE
Slot 2 - PCIe 16 - Son's card *** BRIDGE
Slot 3 - PCIe x16 2.0 - My Card Nr 2

but there's still nothing. Exactly the same.

AFAIK enabling SLI is a matter of drivers. So my second question sounds is it any sense to write to nVidia and ask them to enable 3-way SLI on cards that are signed as 2-way SLI cards ? Not looking at reasons which could be given to them - is it technically possible ?

Thank you.

 

[kylew]

I'm pretty sure XP doesn't support more than 2 GPUs for the purposes of collectively rendering a game.

On top of that, if the cards only have 1 SLi slot each then they'll only be intended to be used in 2 card SLi, they wouldn't work as 3 way SLi.

 

[biuro74]

Sorry, it was checked out on Windows7 - my mistake.

if the cards only have 1 SLi slot each then they'll only be intended to be used in 2 card SLi, they wouldn't work as 3 way SLi.

... and:
"if AMD Phenom II X3 is triple core CPU it will only be intended to be used as 3-core processor, it wouldn't work as 4-core CPU".

Sounds similar for me

http://www.xbitlabs.com/news/video/...dia_s_Focus_for_Now_Says_Chief_Executive.html
(it looks like software issue that haven't been done by Nvidia yet)

 

[MeatLoaf]

Are all 3 cards the same? They also have to be cards with 2 sli fingers such as the 8800GTX or GTX2xx series cards for 3 way to work. Best option you have with single finger cards is SLI + a seperate physx card.

 

[Ch3m1c4L]

i didnt even know it was possible to enable 2 way without a bridge tbh.

 

[biuro74]

Yes, 2-way is possible, but sometimes you've got framedrops (like hi resolutions, hi AA modes - in general: huge data to be transported), and sometimes you've got the same speed (like lower res, or weaker cards).
But I'm not wondering if something clear is possible, but if something unusual can be achieved. Unusual in this case means to get nVidia's drivers ammended to enable 3-way SLI on 2-way SLI cards with no bridge. Probably weaker cards (other than 8800GTX, Ultra, 9800 and G200) are just disabled in code and that's it.