SLi users please come here

[Zenoth]

I wanted to get information from you, gamers, rather than "professionals", about how worth it, how good, or not SLi really is. Some of you might have seen my recent topics and overall disappointments about R600, and that I've decided to switch, at least temporarily (even if it means years) to nVidia. First, I planned to get an 8800GTS 640MB version. But then I thought ... what if I just get two 8800GTS 320MB instead and run them in tandem, a.k.a SLi.

Even with ATi I never touched CrossFire, and since I haven't owned any nVidia cards since 2003 I don't know anything about SLi, since I never needed to. But now I think I should at least know the basics, I should be aware of the facts, the overall known issues (there surely is some, nothing is perfect after all) and all the rest I need to know.

My questions, to start with:

1) Is SLi "forced" upon games ? I.E Are games supposed to be "optimized for" or simply "made for" SLi ? More precisely, let's say I buy 'x' game, and I got my SLi setup, then is it because I got SLi that the game will take advantage of it right away, or is it more like it'll take advantage only if the developers made the game actually support it ?

2) Now, optimizations and compatibilities aside, what kind of performance gains can I expect ? Is there a "universal" gain that any games are seeing when played with SLi ? Here again, will SLi give more performance if the game was optimized for it ?

3) Important one I really need to know: Is there games that will simply never, and can't take any kind of advantage from SLi and will simply detect only a single card even if SLi mode is active ? I.E Old games, for example ... let's say I run UT99, will it take advantage of SLi with a simple "drivers help", or is it condemned to never take advantage of it because ... well, because it's old ? I know what you're going to say, something like "WHO needs to run UT99 in SLi in the first place, that game can be maxed at infinity-high resolutions on G70's and X1K's already". I know that, I just mean on a mere technical point of view.

4) Do both cards need to be of the same brand to run in SLi ? Or do they need to be "the same" as in amount of Memory and/or Frequencies ? (Or anything else to consider ?)

5) Is it safe to run an SLi configuration on 24/7 for weeks non-stop ? Let's pretend nothing is OC'ed, but still on stock coolers.

6) What happens in simple Desktop activities ? Is the second card automatically ... ermmm ... disabled ? I mean is it like electricity doesn't power up the second card at all, completely off ? Or do I need to physically remove it so that it doesn't always run in SLi for nothing ? I mean it's not like I need two G80's to browse Anandtech smoothly Seriously though, is the control over the setup being single-card or SLi software-based or it needs physical intervention ?

7) What do YOU think of YOUR own SLi set-up ? Were you expecting more of it ? Were you entirely disappointed ? Or on the completely opposite, were you in awe and amazement in front of the advantages over a single card setup ? Simply said, was it/is it worth it ? Be honest, please.

That's pretty much about it for my questions, however if you think I missed important points that wouldn't be answered due to the lack of questions for those subjects then please let me know everything I need to. If I ever do it, if I ever buy two of those for SLi, then it'll mean no GPU upgrade for at least two years, and living with a mistake for that amount of time, if not more, wouldn't be good for my sanity. I really need to make sure about it, it's like the biggest, most important purchase/investment of this year for me (well so far it looks like it).

Thanks to everyone for reading, your help, and your time.

 

[Kromis]

1) It is sort of forced. Depends on game profiles, I guess.

2) Don't expect 100% performance increase. Maybe more like...50%-70%? (Arbitrary numbers). Depends on game profiles.

3) Not sure about that...

4) Nope. Just same GPU, thats all that matters.

5) Uhh...no comment

6) Sorry

7) N/A

 

[Matt2]

I'm going to answer your questions based on my 7800GT SLi (God bless it) that I no longer have.

1) It's going to be "forced" sing the SLi profiles. Some games have problems with SLi, but can usually be fixed by altering the rendering mode in the profile, or through updated drivers.

2) There is no universal gain you can expect. SLi is going to give you anywhere from 0% to 95% performance increases. The best part about SLi IMO, is not the increase in average frame rates, but the increase in minimum frame rates.

3) Not sure about this either. Never ran any old games. AFAIK, SLi is done completely through the drivers via profiles and the game does not need to support SLi in any way. You can probably create a profile for your older games and force AFR pr SFR. You might not see huge gains, but it should work.

4) They can be different brand, and they can also be different speeds. The faster card will automatically clock down to the speed of the slower card.

5) It is safe as long as your cards remain within their tolerable temps. Pick your cooling solutions carefully. Keep in mind, the top card will always be hotter than the bottom.

6) No, it wont be disabled. You'll have to take the card out to save power.

7) I loved it. You should watch out for Vsync issues. If you're sensitive to screen tearing, then SLi is not for you.

 

[Zenoth]

Originally posted by: Matt2
I'm going to answer your questions based on my 7800GT SLi (God bless it) that I no longer have.

1) It's going to be "forced" sing the SLi profiles. Some games have problems with SLi, but can usually be fixed by altering the rendering mode in the profile, or through updated drivers.

2) There is no universal gain you can expect. SLi is going to give you anywhere from 0% to 95% performance increases. The best part about SLi IMO, is not the increase in average frame rates, but the increase in minimum frame rates.

3) Not sure about this either. Never ran any old games. AFAIK, SLi is done completely through the drivers via profiles and the game does not need to support SLi in any way. You can probably create a profile for your older games and force AFR pr SFR. You might not see huge gains, but it should work.

4) They can be different brand, and they can also be different speeds. The faster card will automatically clock down to the speed of the slower card.

5) It is safe as long as your cards remain within their tolerable temps. Pick your cooling solutions carefully. Keep in mind, the top card will always be hotter than the bottom.

6) No, it wont be disabled. You'll have to take the card out to save power.

7) I loved it. You should watch out for Vsync issues. If you're sensitive to screen tearing, then SLi is not for you.

Thank you Matt and Kromis as well for your suggestions and advices.

About VSync, I never used it once with ATi since I rarely saw my game's overall FPS going above my Monitor's Refresh Rate, which is set at 100Hz, so basically before I see tearing in my games then it'll have to run above 100 FPS ... which I can tell you never happened on my current rig EXCEPT for Source-based games which are optimized to the top, and very old games which I don't play often if ever.

But technically speaking, if I ever encounter any such VSync-related issues, then should it be fixed by nVidia anyway via driver updates ? They can't just leave their consumers behind in the dust experiencing heavy tearing problems in games, especially considering the amount of money (usually high enough) for a SLi setup. Well at least I hope so.

On a side note, I'll get my GTS this upcoming week-end

 

[AVP]

I don't mean to be off topic here, but you are considering two 320's over a 640 though their memory will not combine in SLI. Also I would get a gtx over two 320s, they come out to be about the same price, $520 vs $530 (gtx). The gtx should be faster overall especially at higher resolutions...

 

[m21s]

Originally posted by: AVP
The gtx should be faster overall especially at higher resolutions...

+ You don't have to worry about SLI problems (Vsync and having correct profiles)

And

Requires less power

 

[Tsunami982]

I second the idea of buying 1 single faster 8800GTX. I had 2 7900gt's SLI'ed in a watercooled setup a while back and realized it wasn't quite worth it. In my own experience, I usually saw gains of about 0-50% (even in games designed for SLI). If it doesnt say designed for SLI, assume you will be getting 0% gain. I think 3Dmark06 is the only thing that gave me a good increase (41xx to 76xx) dont really remember the numbers.

I would recommend SLI only if you really really need the cutting edge of speed. There are a lot of other considerations you have to take into account when SLI'ing. Can your power supply cut it? Does your motherboard have 2 PCIE 16x slots (most people assume since they have an SLI board that they have 2 16x slots but the vast majority of boards don't)? Do you need those extra slots (besides taking up the extra pcie slot the coolers from those video cards will usually take up the slot below as well)? Are there cheaper components that you can upgrade first that will give you more bang for buck (although video cards usually bear the brunt of most games nowadays, CPU, RAM, and even hard drive play a part too and are usually much cheaper than 2 $300 video cards)?

To answer your more specific questions: it does not automatically power down (to power down you need to physically take it out). doesnt need to be same brand but its a good idea since different company's tweak their cards a bit. safe to run them 24/7 if you have adequate airflow (most 8800gts' blow air straight out the back anyway).

To reiterate my most important point... BUY ONE 8800GTX unless you absolutely need the speed. Just my thoughts.

 

[josh6079]

They can't just leave their consumers behind in the dust experiencing heavy tearing problems in games, especially considering the amount of money (usually high enough) for a SLi setup.

I wouldn't say that they, "...left their consumers behind in the dust", but it did seem to be a persistant problem with my 7800 GT SLi setup I had. Disable vsync and I had fluid frames with torn graphics, enabled vsync and I had choppy frames with a uniform graphics. At the time I had to pick my poison and simply go without vsync, and depending on the game it's not so bad. However, at the time I was playing FEAR and for the areas where lights were flickering the combination of having screen tearing and strobe light effects weren't pleasant.

That was with the 7 series though. I haven't heard much in the way of the 8 series' SLi performance and quality issues. Last I heard, SLi AA didn't even work, but that may have been fixed.

 

[Zenoth]

Thank you all, I'm taking lots of notes about all this.

As I said guys, I'm considering SLi, I won't be getting a second GTS until at least two or three extra months from now, or even more. And I don't have the money for a GTX at the moment, only one GTS and that's it. I need to upgrade, my system cries for a GPU change, and I'm tired to play my games (recent ones at least) at lower resolutions than I could be running them at, and with lower settings. So, right now (well, next week end) I'll get my GTS, and I'll get a 640MB version, finally. And then, maybe by the end of this summer I'll get a second one, which I hope so will have had the time to decrease in price a little.

 

[aka1nas]

You might be better off getting an EVGA GTS 640MB model and using the step-up if they come out with a faster refresh part or even just to step up to a GTX.

Edit: BTW, the general consensus here when I asked was that the PSU we both have will NOT be sufficient for GTS SLI and an OC'ed CPU.

 

[MarcVenice]

@tsunami, you don't need 2 pci-e 16x slots for SLI to thrive. Right here you can see what performance gain some newer games get from SLI mode, and how the pci-e slots being 8x or 16x doesn't really matter at all ...

And I definately think that getting a second card to put them in SLI later on, if you can't afford 2 right now, is a viable option. But at that time when you need a second card, or can afford it, buying a new, better, one, might even be a better option.

 

[rise]

Originally posted by: Zenoth
Thank you all, I'm taking lots of notes about all this.

As I said guys, I'm considering SLi, I won't be getting a second GTS until at least two or three extra months from now, or even more. And I don't have the money for a GTX at the moment, only one GTS and that's it. I need to upgrade, my system cries for a GPU change, and I'm tired to play my games (recent ones at least) at lower resolutions than I could be running them at, and with lower settings. So, right now (well, next week end) I'll get my GTS, and I'll get a 640MB version, finally. And then, maybe by the end of this summer I'll get a second one, which I hope so will have had the time to decrease in price a little.

i've had a gts 640 since about launch and i'll probably adding another in a month or so. i will buy from evga as i'll try to buy close enough to nv's refresh card launch so that i can step-up and stay with one card if the performance is there.

i'd rather a one-card solution but i also have never tried sli and this looks like a good time to try.

profiles, power consumption, well, lets face it, everything but actual performance is kind of a nuisance with sli but i'll probably try it.

 

[Zenoth]

Thanks once more guys for all your input.

About the PSU, I was also planning to change it when the time comes for my SLi setup, I will surely buy it the same day than my second GTS. I will try my best to get an e-VGA (well, the vendor will, not me), but according to what he told me it'll be either that, or more likely an ASUS version, since his distributor doesn't have any BFG's or Leadtek's in stock, only ASUS' and e-VGA's for now, and it seems that e-VGA's are only 320MB versions, but he isn't sure, I will know Friday if it'll be ASUS or e-VGA, 640MB, that is.

 

[Doctahg]

If you do SLI..download nHancer. it provides MANY SLI profiles for all games, with the optimized settings for each game. Check it out. They have a forum as well.
Doc

 

[terentenet]

Here are answers based on personal observations:

1.

Is SLi "forced" upon games ? I.E Are games supposed to be "optimized for" or simply "made for" SLi ? More precisely, let's say I buy 'x' game, and I got my SLi setup, then is it because I got SLi that the game will take advantage of it right away, or is it more like it'll take advantage only if the developers made the game actually support it ?

SLI is forced upon games via drivers/app. profiles. You can also alter the profiles, select the rendring mode and much more.

2.

Now, optimizations and compatibilities aside, what kind of performance gains can I expect ? Is there a "universal" gain that any games are seeing when played with SLi ? Here again, will SLi give more performance if the game was optimized for it ?

There's no universal gain. You can gain 0%, you can gain 90-95%. It all depends on the profile and how graphical intensive is the game. Some games dont like SLI.
Some games are just CPU limited. SLI won't help there. FPS will be the same. But, push the eye candy to the maximum and you should see some gains from SLI.

3.

Important one I really need to know: Is there games that will simply never, and can't take any kind of advantage from SLi and will simply detect only a single card even if SLi mode is active ? I.E Old games, for example ... let's say I run UT99, will it take advantage of SLi with a simple "drivers help", or is it condemned to never take advantage of it because ... well, because it's old ? I know what you're going to say, something like "WHO needs to run UT99 in SLi in the first place, that game can be maxed at infinity-high resolutions on G70's and X1K's already". I know that, I just mean on a mere technical point of view.

Everything can work in SLI. You can select dual GPU mode even for the desktop if you wish. If there's an app/game that doesnt have a SLI profile, you can create one yourself.
Do you know the Winamp vis. plugin named Milkdrop? I created a SLI profile for that. So yeah, you can use SLI for whatever you want.

4.

Do both cards need to be of the same brand to run in SLi ? Or do they need to be "the same" as in amount of Memory and/or Frequencies ? (Or anything else to consider ?)

No any 2 cards with same GPU will do. The cards being identical (same brand/model; clocks) is optimal and might save you some headaches.

5.

Is it safe to run an SLi configuration on 24/7 for weeks non-stop ? Let's pretend nothing is OC'ed, but still on stock coolers.

Yes, you can run it 24/7 without a problem. Take care though, GPUs tend to get very hot these days. Running SLI won't get them (much) hotter, but you might want good airflow.

6.

What happens in simple Desktop activities ? Is the second card automatically ... ermmm ... disabled ? I mean is it like electricity doesn't power up the second card at all, completely off ? Or do I need to physically remove it so that it doesn't always run in SLi for nothing ? I mean it's not like I need two G80's to browse Anandtech smoothly Seriously though, is the control over the setup being single-card or SLi software-based or it needs physical intervention ?

One card will be used, 2nd will idle. The idle card will consume current, it cannot be stopped.

7.

What do YOU think of YOUR own SLi set-up ? Were you expecting more of it ? Were you entirely disappointed ? Or on the completely opposite, were you in awe and amazement in front of the advantages over a single card setup ? Simply said, was it/is it worth it ? Be honest, please.

This is my 3rd SLI setup. So, if I'm still using SLI, it means I'm happy with it. I had my share of problems at the beginning but I learned how to fix them. SLI is not that hard to do and use. Nvidia advertises it and wants users to adopt it, so you know you'll have your support.


I don't know what's better though. 1 8800GTX or 2 8800GTS 320Mb in SLI. I'd go SLI. Minimum frame rates should be better.
There are few to no games that DONT take advantage of SLI.

As advice, replace the 320Mb with 2 8800GTS 640Mb and you have a winner.

 

[Zenoth]

Thank you very much terentenet, and everyone else again. Much appreciated. I literally printed this whole thread hehe, kinda tired to write down information on paper myself, technology is there for the lazy, so why not use it ?

Well, I got my GTS 640MB yesterday, so, yeah, a 640MB version will help me. I tried many of my games so far and even though my CPU does bottleneck the card it still gives around 90% to 120% performance increase over my X1800XL 256MB. And I repeat, that's with a bottleneck, which I read on another discussion forum seems to be non-negligible, quite significant in fact. So I wouldn't even imagine if I got some Core 2 Duo's, or Penryn's or Barcelona's with this beast, it'd fly sky high, although it already does in my book anyways.

There, on my old set-up, with the X1800XL, OC'ed at 540/640 I scored 4179 in 3DMark06, at default settings.

Now, same set-up except for the GPU, my new GTS, scored 8244, at stock speeds (513/792).

Then, I OC'ed it a little, to 560/850 and I scored 8548.

So far from what I've read and observed (especially at Futuremark.com after searching tons of results from very similar systems) it looks like only the Intel's C2D can really "push" such a card as the GTS and surely even the GTX and also the HD 2900XT, to their potential limits. Also I need to consider that I'm still on Socket 939 with 400Mhz (PC-3200) Memory, so it's kinda old technology, but it does the job well. I mean, if I would have had the choice to get some Dual or Quad Core C2D over my current X2 (also by changing the Mobo and Memory of course) I'm pretty confident that it would have never literally doubled the performance across the board. I knew that a single GPU upgrade while still keeping the rest of my system intact would bring some major benefits even with a significant bottleneck on my path. And that's what happened ! I'm very happy with my purchase. Now all I want is my no-yet-released-but-soon-to-come Zalman VF-1000, so that I can hear sounds coming from my games and not just the fan noise.

 

[Matt2]

Originally posted by: Zenoth
Thank you very much terentenet, and everyone else again. Much appreciated. I literally printed this whole thread hehe, kinda tired to write down information on paper myself, technology is there for the lazy, so why not use it ?

Well, I got my GTS 640MB yesterday, so, yeah, a 640MB version will help me. I tried many of my games so far and even though my CPU does bottleneck the card it still gives around 90% to 120% performance increase over my X1800XL 256MB. And I repeat, that's with a bottleneck, which I read on another discussion forum seems to be non-negligible, quite significant in fact. So I wouldn't even imagine if I got some Core 2 Duo's, or Penryn's or Barcelona's with this beast, it'd fly sky high, although it already does in my book anyways.

There, on my old set-up, with the X1800XL, OC'ed at 540/640 I scored 4179 in 3DMark06, at default settings.

Now, same set-up except for the GPU, my new GTS, scored 8244, at stock speeds (513/792).

Then, I OC'ed it a little, to 560/850 and I scored 8548.

So far from what I've read and observed (especially at Futuremark.com after searching tons of results from very similar systems) it looks like only the Intel's C2D can really "push" such a card as the GTS and surely even the GTX and also the HD 2900XT, to their potential limits. Also I need to consider that I'm still on Socket 939 with 400Mhz (PC-3200) Memory, so it's kinda old technology, but it does the job well. I mean, if I would have had the choice to get some Dual or Quad Core C2D over my current X2 (also by changing the Mobo and Memory of course) I'm pretty confident that it would have never literally doubled the performance across the board. I knew that a single GPU upgrade while still keeping the rest of my system intact would bring some major benefits even with a significant bottleneck on my path. And that's what happened ! I'm very happy with my purchase. Now all I want is my no-yet-released-but-soon-to-come Zalman VF-1000, so that I can hear sounds coming from my games and not just the fan noise.

You're right, a CPU upgrade is silly when your most pressing need is a GPU.

Have you tried to OC that 4400+ any further? Should do 2.7 pretty easily.

 

[Zenoth]

Yes I tried.

If you knew the story behind my attempts, no matter what I tried, what others told me to do (I must have asked in 10+ forums within the past five months), the best I can OC it to without instability issues is 2.4Ghz, and the Memory refuses to operate above 442Mhz, no matter the divider, no matter the DDR Voltages, no matter the Chipset Voltages or Command Rate speed ... no matter what I tried, it starts having all sorts of issues at exactly 2.48Ghz (it's at 2.42 right now completely stable, running like that 24/7 since months).

As it stands it's entirely stable, Prime95 (two .EXE's) stable for 26 hours, no crashes, no errors, no over-heats. And Orthos as well was stable, along with MemTest for at least 15 hours or so. It's just a very unlucky lemon of an X2 I can tell you. My old 3500+ Winchester OC'ed way better than that.

 

[aka1nas]

Don't meant to hijack Zenoth's thread, but maybe he will find this question useful too:

What is the current deal with SLI and multiple monitors? Are you still limited to one display with SLI enabled? Does this limitation only take effect in games or also when you are just at the desktop? Would a reboot be required each time to switch modes?

 

[deadseasquirrel]

Originally posted by: Zenoth
Well, I got my GTS 640MB yesterday, so, yeah, a 640MB version will help me. I tried many of my games so far and even though my CPU does bottleneck the card it still gives around 90% to 120% performance increase over my X1800XL 256MB. And I repeat, that's with a bottleneck, which I read on another discussion forum seems to be non-negligible, quite significant in fact. So I wouldn't even imagine if I got some Core 2 Duo's, or Penryn's or Barcelona's with this beast, it'd fly sky high, although it already does in my book anyways.

You'd be surprised at how LITTLE of a bottleneck the CPU can be. It really depends on the specific game and what resolution you play at (as well as gaming settings such as AA/AF).

Here, the GTX/GTS tested with the A64 and here is the C2D with the GTX/GTS.

As you can see, it varies across games and settings. But, for example, a GTS 640mb like yours with a X2 3800+ gets 72fps in FEAR at 1280x1024. That only jumps to 81fps with an x6800. Obviously not worth the cost increase.

 

[Zenoth]

Very interesting deadseasquirrel ! Thanks for that information.

However, bottleneck or not, I was planning for a system upgrade by the end of summer of this year. Now that I've got my new GPU, all I need is a new Motherboard (awaiting AM2+), a new CPU (awaiting Barcelona) and new Memory (DDR2 or DDR3, I will see when the time comes). And much later this year or early next year, a new PSU for a potential SLi set-up or a better single GPU in late 2008 or somewhere in 2009. And for those wondering why I like to stay with AMD as far as CPU's are concerned, is simply because I get 30% discounts on those products, thanks to a very, very good friend of mine. I've always been curious about Intel's C2D technology, and I still am, but where money is saved is where a man is happy

 

[deadseasquirrel]

Yes, C2D is a very good chip (and I could very well upgrade to one soon myself), but, like you said, anywhere you can save money...

Like you, I am planning an end-of-the-summer upgrade. But, unlike you, I haven't completely decided AMD or Intel. Both appear to have good future upgrade options with some caveat gotchas (such as Penryn not working with some current mobos or Barcelona's AM2 vs AM2+ thing).

I guess, for me, it's going to come down to what looks like the best path at the time when I actually have money for the upgrade. If it's early September and Barcelona is nowhere in sight and I'm actually ready for quad, I'll go with the Q6600 path and try to choose a mobo that will have an upgrade future to Penryn. If I'm not quite ready to take advantage of quad, I could very easily go AM2 on the cheap and have a future path for Barcelona.

Either way, it's about 3 months away for me and anything can happen in that time. Plus, I'm waiting for new GPU options. R600 isn't it right now with the drivers in the state they are in. And I like the GTX, but don't want to pay the premium for it. So, hopefully, by that time, GTX-like power will be available for sub-$400. I'll need to do a sub-$1000 build (need a case w/o psu, mobo, 2GB DDR2, GTX-like GPU, CPU, new HDD).