SLI / CrossFire FAQs

[Maziar]

After reading some lines from the article and your reply "Yes, it can be achieved, but VRAM limitations can sometimes get in the way, as in the future, more VRAM may be needed to run games well.", I've been thinking quite a lot about what does it mean.
First I took it as: "If you SLI 2gb and 4gb card, 4gb card will become 2gb, and total memory will be 2gb nontheless".
After reading theads like http://www.tomshardware.co.uk/answers/id-1857498/sli-760s-4gb-utilize-4gb-vram.html \ http://www.tomshardware.co.uk/answers/id-1857056/gtx-770-4gb-2gb-vram-sli.html ,
I may think that you meant that SLI 2gb+4gb will not be 6 gb, but 4(2+(4\2))gb. I do feel like 2gb is not really future-proof(those theads say that even modern mods and graphics sometimes favor 2gb+), but I thought that if I can't really push 4gb card now, should I go for decent 2gb card to SLI it later?

Since I would also like to stick with Nvidia, GTX760 for a couple of years, because it alone supports PhysX(althought I've read that later both greens and reds will share some similar technology to relieve customers from this torturous decision), and because benches at THW show GTX being superior to it's counterpart HD7950 in everything, but bitcoin, obviously.

I remember from the article that AMD can XF 2+4gb cards fine, just 4gb will be scaled down, and that Nvidia on the other hand - can't, without specific soft or something.

So the question is: will SLI of GTX760 2gb + GTX760 2gb(possibly different manufacturers, but otherwise same models) make it total of 4gb, or still 2?

2GB

 

[bystander]

After reading some lines from the article and your reply "Yes, it can be achieved, but VRAM limitations can sometimes get in the way, as in the future, more VRAM may be needed to run games well.", I've been thinking quite a lot about what does it mean.
First I took it as: "If you SLI 2gb and 4gb card, 4gb card will become 2gb, and total memory will be 2gb nontheless".
After reading theads like http://www.tomshardware.co.uk/answers/id-1857498/sli-760s-4gb-utilize-4gb-vram.html \ http://www.tomshardware.co.uk/answers/id-1857056/gtx-770-4gb-2gb-vram-sli.html ,
I may think that you meant that SLI 2gb+4gb will not be 6 gb, but 4(2+(4\2))gb. I do feel like 2gb is not really future-proof(those theads say that even modern mods and graphics sometimes favor 2gb+), but I thought that if I can't really push 4gb card now, should I go for decent 2gb card to SLI it later?

Since I would also like to stick with Nvidia, GTX760 for a couple of years, because it alone supports PhysX(althought I've read that later both greens and reds will share some similar technology to relieve customers from this torturous decision), and because benches at THW show GTX being superior to it's counterpart HD7950 in everything, but bitcoin, obviously.

I remember from the article that AMD can XF 2+4gb cards fine, just 4gb will be scaled down, and that Nvidia on the other hand - can't, without specific soft or something.

So the question is: will SLI of GTX760 2gb + GTX760 2gb(possibly different manufacturers, but otherwise same models) make it total of 4gb, or still 2?

In AFR (alternate frame rendering), each card must render a full frame on their own, and their for need to load all the same stuff in VRAM as any other card in SLI/CF. As a result, you do not gain any benefit in terms of additional VRAM from multiple cards. You effectively are operating as if you have 2 card worth of VRAM, and it will operate as if you had which ever card has the least amount of VRAM.

When SLI and CF were new, there were other methods employed which may have gained some benefits, but did not give you nearly as good of scaling. These methods included splitting the screen in half and having each card only render half a screen. However, these methods are no longer used today.

 

[Wrathinside]

If SLI\CF pretty much screws up VRAM, then I read that to select another GPU to process PhysX, there is no bridge required. How does it work? Is it considered SLI\CF, or it's something else, but still supported by drivers?
Also - is it possible to use both Nvidia and AMD this way? So that Nvidia would manage PhysX and AMD would do the rest? Or there are no official drivers that could support this?
I understand that SLI\CF sum up the performances, so bridge-less PhysX GPU would not do anything for perforance, except for providing PhysX. I've also seen a vid, where a rather old card doing PhysX for something like 680x even reduced 680x' performance instead of improving it. That essentially means that card added will not make any benefit, if it doesn't do it's job as good as master card?
Also, I think I've heard tha if GPU runs out of VRAM - it takes from RAM, probably virtual memory, not sure. Is it possible to recompense for lack of VRAM by having plenty of RAM?
I just don't see the point in pushing 4gb version of technically 2gb card for future hopes of either multiscreen or super heavy games(which I don't play), but I don't see how can I use a 2gb GPU later, when I buy some newer and, hopefully, more-RAM filled GPU for multiscreen.

 

[kakscy]

Thank you it was very helpfull!

 

[asd12]

Can i put gtx760 hawk and gygabyte gtx 780 in sli ?

 

[Maziar]

Can i put gtx760 hawk and gygabyte gtx 780 in sli ?

No

 

[sickbullet]

Tried crossfire for the first time and it was an utter nightmare I bought a second a 7970 same speeds and model, and sold it back on the next day

So going to get a 290X when the other branded coolers come.

 

[asd12]

hi can i put gtx 690 and 770 in sli cs they have the same gpu if not which sli do u more recommend
ty

 

[krayzier1]

XFX Radeon HD 7970 black is compatible with the other in its range HD 7970 for CF?
seems your saying that as long as the GDDR is same and the speed is aits full steam ahead ? am i right ?...and how will this play out for the OC on the black edition ?

Yes,it'll work fine

if this has already been addressed I am sorry.. I just need some help now..

I have a problem.. I have 600 bucks worth of cards and they don't perform.. I have two MSI N560GTX-Ti Twin Frozr II 2GD5/OC.. with 2GB.. I have a i-7 2600K CPU and a GIGABYTE GA-Z68XP-UD3 motherboard.. Running 16 GB Ram (2X Crucial Ballistix Sport 8GB. I also am running two Chronos SSD as well as 2 1 TB WD sata 6 drives.. I have a 680 watt APEVIA ATX-AS680W-BL 680W.

I can run one card and it crushes the two in SLI.. Can anyone tell me why? Seems afterburner telles me second card has 0% GPU use..

Probably one of your cards is defective,test them simultaneously to see if they work or not

can you crossfire HIS Radeon HD 7970 X2 with r7970 black edition? are they still in the same family as there 2xs?

You mean 3-way CF ? is so,then yes

Hmmm, Clears up some queries i had with Crossfire, nice one.

Glad it helped

hi can i put gtx 690 and 770 in sli cs they have the same gpu if not which sli do u more recommend
ty

Ty for your reply

 

[HogCooter]

Stupid question but does crossfire improve Frame Rate? I am looking to get another SAPPHIRE Vapor-X Radeon HD 7770 and wonder if it will actually improve gaming. From what I read, the main advantage is a power issue. Will the difference be noticeable? Any comments?

 

[nukemaster]

Both Crossfire and SLI are designed to improve performance. This includes frame rates. AMD has been working to get more consistent frame times out of its cards with newer drivers.

So if you go this path, ensure you have the latest drivers.

Sometimes a single faster card is more desirable due to power and space concerns as well as more consistent performance(some games do not scale as well with multiple cards.).

 

[HogCooter]

Thanks Nuke!

 

[BRANDON DAVIS]

This is more like my question, and this thread seems to be the right place to ask (I've made it through only the FAQ and the first three pages, so far lol ...but have a pressing need to get an answer, due to the sales this month). If I'm in the wrong place, do please let me know.

New build. Main board is Gigabyte GA-990FXA-UD3 (will arrive this week). Also purchased an XFX FX-785A-ZNL4 (HD 7850) ...$119 w/the rebate.

Should I buy a second XFX while they're on sale and CF 'em? IOW, is that going to be a well-spent $238 (i.e., $119x2 cards) for the performance (from what I've read, there does seem to be a performance advantage)? Or not? (I'll have my bro' purchase the 2nd XFX, so I'd get the rebate for the second card too.)

...even with a second 7850, my total build price (w/new everything), is going to be just under $800 (w/ an FX8320, 250+120GB SSD, 630W 80+ bronze, case, and 16GB RAM), so it's certainly a "budget build" as I understand it (be nice: I'm old lol, and haven't DIY'd a system in a decade). I still have an unused W7 license, though I'm not sure if I won't just install Linux, and run W7 as a VM (I do a lot of VM's for support reasons: my "day job").

(I run a minimum of four displays for various, non-gaming reasons with the main display at 1920x1200, and others at lesser res's ...that will be changing this coming year to all 1920x1200 minimum ...still not sure which direction I'm going to go.)

TIA.

...my first question on Tom's ever btw (though I've been reading the forums for ...idk, the past 10 years at least).

 

[nukemaster]

If you do not plan to game, You do not even need to get another 7850, you can even get something like a 7770 or 7750 just to run extra screens.

Each card should run 3 screens if one is Display Port. Having 2 should allow 2 analog + 2 digital not including the 2 Display Port options you still have or 4 Digital(HDMI/DVI) without issues.

2 7850's in crossfire should give a decent performance boost, but you will need the latest drivers and AMD is still working out driver issues with multi screen crossfire performance on some cards.

The chart on Tom's in the following link while old, gives you an idea what 2 x 7850's in crossfire will do, but again it is important to know that newer articles have show frame pace issues[high fps reported by games, but jumpy graphics due to partial frames or even frames that do not make it to the monitor] that are being addressed in current and newer drivers. It may still be a while for AMD to get all the bugs worked out(the fixes are underway for sure).
http://www.tomshardware.com/reviews/geforce-gtx-660-geforce-gtx-650-benchmark,3297-14.html

 

[BRANDON DAVIS]

If you do not plan to game, You do not even need to get another 7850, you can even get something like a 7770 or 7750 just to run extra screens.

Each card should run 3 screens if one is Display Port. Having 2 should allow 2 analog + 2 digital not including the 2 Display Port options you still have or 4 Digital(HDMI/DVI) without issues.

2 7850's in crossfire should give a decent performance boost, but you will need the latest drivers and AMD is still working out driver issues with multi screen crossfire performance on some cards.

The chart on Tom's in the following link while old, gives you an idea what 2 x 7850's in crossfire will do, but again it is important to know that newer articles have show frame pace issues[high fps reported by games, but jumpy graphics due to partial frames or even frames that do not make it to the monitor] that are being addressed in current and newer drivers. It may still be a while for AMD to get all the bugs worked out(the fixes are underway for sure).
http://www.tomshardware.com/reviews/geforce-gtx-660-geforce-gtx-650-benchmark,3297-14.html

Thank you nukemaster. I will check out that link.

I think this card does support four displays btw ...but I may want to up that to six (or 3-4 with much higher resolution, and perhaps physically larger) displays, so for that reason, it might be justified?

...my productivity usually increases with more and/or better displays (so I can pretty much justify the expense ...plus my current displays are pretty old at this point, and I recall reading something about all the ones of this technological "era" having some kind of burn-out/end-of-life issues sooner than later).

...but I would like to be able to occasionally run a game as far as that goes (the last game I played was probably Quake or something: life has gotten really busy since then, but it's slowing down again, so maybe I can dip my feet back in the pool lol).

So for a $120 "upgrade": worth it?

UPDATE: You already answered the question, lol. Brilliant! Looking at the chart, and comparing a single 7850 with dual 7850's in CF, it seems that - for gaming - CFing with a second 7850 isn't that bad an idea. Thanks!

 

[Maziar]

hi can i put gtx 690 and 770 in sli cs they have the same gpu if not which sli do u more recommend
ty

No you can't and they don't have the same GPU core. You can SLI 690 with a 690 and 770 with another 770

 

[Resetes12]

If I Crossfire a Sapphire R9 270x Dual-x 4Gb (principal GPU) with a 2Gb version (secondary GPU) I will get 4Gb or 2Gb of VRAM?

Thanks in advance.

 

[nukemaster]

The usable vram will be that of the lower memory card. so you will have 2gigabytes. This is because all data has to be on both cards.

 

[Roadsguy]

You should add something about SLI/Crossfiring between a CPU w/ graphics and a compatible GPU. I hear it's possible to do this.

Also, ATI in the OP should be changed to AMD to minimize confusion as well as making it not look so stale.

 

[nukemaster]

Crossfire with cpu graphics is rather unimpressive when a single lower end card may be as fast.

The cart has actually not been updated by AMD yet so that is why it stops at the 7970.

I am sure Maziar may well update this in the future(for sure when AMD adds a new chart, maybe they do not want to tell people that a R9 280X can be combined the rebranded cards can be crossfired with the card they have been rebranded from), but they have been rather busy lately.

 

[Maziar]

Yes,like I said before,I'm going to update the chart(massively).Just need a little more time and I hope AMD update their CF charts soon

 

[Pexon011]

Hello ,what should i buy ,at the moment i am using nvidia 560ti and i am thinking of putting one more in sli ,or to buy nvidia 660ti

tnx for help

"Post edited by Maziar,reason: "No advertising here"

 

[TheDoubleD]

Hello. I have a Sapphire 7870 XT and I would like to upgrade by crossfiring it. With what GPU should I crossfire it? I know it can be crossfired with either another 7870 xt or 7950. Up here where I live, they have almost the same price, but should I really crossfire with 7950 when all their stats are different (like gpu clock, memory, memory clock, bit rate)? What would be the side effect of this?

 

[wh3resmycar]

hi guys, is hypersli still serviceable on non sli motherboards?

 

[Maziar]

Hello ,what should i buy ,at the moment i am using nvidia 560ti and i am thinking of putting one more in sli ,or to buy nvidia 660ti

tnx for help

"Post edited by Maziar,reason: "No advertising here"

2 560Ti's will be notably faster than 1 660Ti

Hello. I have a Sapphire 7870 XT and I would like to upgrade by crossfiring it. With what GPU should I crossfire it? I know it can be crossfired with either another 7870 xt or 7950. Up here where I live, they have almost the same price, but should I really crossfire with 7950 when all their stats are different (like gpu clock, memory, memory clock, bit rate)? What would be the side effect of this?

"One of the cards will raise/lower its clock speeds to reach the other card's speeds."
So I recommend getting the exact same model of the card you have

hi guys, is hypersli still serviceable on non sli motherboards?

It seems it's no longer possible
http://www.techpowerup.com/forums/threads/hypersli-enabling-sli-on-non-sli-motherboards.153046/