SLI Doesn't Always Net Gains Over Having Just One Card

[trowand]

Hey, I had heard this before but just saw it again in the latest issue of ExtremeTech by PC Magazine. They tested a bunch of SLI and non-SLI machines in games and benchmarks and some games didn't get any FPS boost from SLI. It sure would stink to spend $400-$600 on that second graphics card only to find that it nets you no gain at all. 3DMark05 seemed to gain the most from SLI with about a 40-45% gain. Doom3 only gained about 25% while Half Life 2 gained about 10-15%. Unreal Tournament 2004 gained almost NOTHING as did Flight Sim 2004. The SLI difference was most noticeable when cranking up the eye candy such as AA and AF. :eek:

[Force Flow]

It all depends on how powerful or weak the cards are and how graphic-dependant the games are. Making a generalization like that "SLI offers almost no net gain" doesn't really mean a whole heck of a lot.

[rspassey]

Well if you have SLI you get less stress on each card, therefore you can crank up the settings to max. I can tell the improvement with SLI in my rig than when I run without SLI.

[TwoRails]

And I'd guess some of that is that most games don't need that much power yet, meaning if game runs pretty good maxed out on AGP, then certainly SLI won't give any performance increase.

[Jaggannath]

Yup... if they find that in a years time I'll be interested, but at the moment I don't feel it demonstrates much.

[trowand]

I myself would GREATLY prefer to have just one card in my system than two. Of course I want that one card to be super fast thus giving me SLI like performance but one card = less heat, less voltage, more room, better airflow and of course an extra $500 in your pocket. I wish the industry would completely drop the dual graphics card idea completely and just make faster single cards. I believe that it's just a way for the GPU manufacturers to suck more money out of us gamers and enthusiasts. :mad:

[Force Flow]

And I'd guess some of that is that most games don't need that much power yet, meaning if game runs pretty good maxed out on AGP, then certainly SLI won't give any performance increase.
Correct.

If there was a compariston between running a single 6600 and dual 6600's, the dual setup would win.

But, if there was a compariston between running a single 7800 and dual 7800's, you wouldn't notice a difference because the rendering power isn't needed.

If you have not yet read the SLI technology article, here's a blurb pertaining to this question. http://www.pcmech.com/show/internal/817/6/

It may be slightly cheaper to get two weaker cards paired off with SLI, but ultimately, the overall performance usually turns out to be far better with a single all-powerful card. It's the same with any piece of hardware. RAM, for example, usually runs a bit better with one large stick, rather than two or more smaller sticks.

If you do go with an all-powerful card, later down the road when it's time for an upgrade, you could probably get that same card for about half the price, install it in the SLI setup, and nearly double the performance, thus extending the life of your gaming machine. Remember, if there are powerful cards running in SLI configurations, very few games actually utilize that graphics power. Some of the more resource dependant games are CPU-bound, rather than graphics card dependant because of the hefty physics calculations required, such as in Doom 3 and Half-Life 2, and most notably in Half-Life 2: Deathmatch. Using this technology for future upgrades, rather than obtaining dual video cards immediately is a bit more practical. After all, it was originally 3dfx's intention.

[Jaggannath]

Nice find with that article FF... proof of what I suspected

[Snod Blatter]

Voodoo2's rule!

Now that I've got that out of my system, I would like to say that I really think they should've found some way of making the SLI in hardware rather than being controlled in software.

Also, as has been said, games today are really CPU limited... maybe SLI will become better when games are 64-bit?

Anyway... SLI today is just silly if you ask me... the cards take way too much juice to power and give out way too much heat for there to be 2 of them in a system.

Maybe we'll be going mad for SLI setups in a few years though, when CPU's are much faster (or at least they should be), but right now... there's no need for it.

[Force Flow]

Now that I've got that out of my system, I would like to say that I really think they should've found some way of making the SLI in hardware rather than being controlled in software.
I disagree. That would mean you would be locked into a set of features and bugs. Imagine if the drivers for video cards were all hard coded.

Anyway... SLI today is just silly if you ask me... the cards take way too much juice to power and give out way too much heat for there to be 2 of them in a system.
If you plan well, this wouldn't be an issue.

Maybe we'll be going mad for SLI setups in a few years though, when CPU's are much faster (or at least they should be), but right now... there's no need for it.
SLI technology is meant as a route for upgrates, like was mentioned in the article.

[Snod Blatter]

How many features do you want? I'd be happy just with being able to use 2 cards instead of 1...

And by power consumption I mean paying for the electricity bill, too :)

[weremonkey]

SLI interface w/ 2 quality video cards will outperform 1. But 1 quality video card will out perform a low-end SLI interface. And like ryan said, having 2 will put less strain on each one, meaning they will produce less heat.

[Yuanji]

all of the games you listed so far are all CPU bound. Mark05 is only CPU bound with 7800s. UT2004 is extremely CPU bound and so is flight sim. HL2 is also a very CPU intensive game. You'll find that games such as BF2 which are more GPU limited get a huge benefit from SLi

[rspassey]

all of the games you listed so far are all CPU bound. Mark05 is only CPU bound with 7800s. UT2004 is extremely CPU bound and so is flight sim. HL2 is also a very CPU intensive game. You'll find that games such as BF2 which are more GPU limited get a huge benefit from SLi

Good point, I didn't even thing of that. In some games the CPU does most of the work, where as in other games the load is put on the GPUs.

[Force Flow]

SLI interface w/ 2 quality video cards will outperform 1. But 1 quality video card will out perform a low-end SLI interface. And like ryan said, having 2 will put less strain on each one, meaning they will produce less heat.
It's not the quality that matters in terms of performance...it's the clock speeds. Yes, quality *is* important, but not in the context in which you are using it.

Remember, with dual video cards, you aren't getting a fully doubled boost in performance. You're only getting a range of 1.5 to 1.8 times greater than the single card.

It doesn't have anything to do with strain either, the load is balanced equally between the two cards. One card doesn't do more work than the other.


Most of what I've been saying in this thread is all covered in the SLI Technology guide, found here:http://pcmech.com/show/internal/817/

[guitarwolf]

i ws thinking of getting 2 geforce 6800GT cards, but am now thinking of just getting a single Geforce 7800GT card.
i'll have an SLI mobo, so i can always grab another 7800GT later on when the price drops and more games need it.

just a question...would running a single card on an SLI mobo have any affect on performance? what i'm asking, i guess, is, does a SLI mobo perform like a normal mobo with only 1 card in it.

the mobo in question is Asus A8N-SLI Deluxe (or premium...i haven't decided yet).

thanks!

[Force Flow]

i ws thinking of getting 2 geforce 6800GT cards, but am now thinking of just getting a single Geforce 7800GT card.
i'll have an SLI mobo, so i can always grab another 7800GT later on when the price drops and more games need it.
That's the concept in practice exactly. :) Grab the 7800GT

Yes, SLI motherboards can run either single or dual cards. It will operate normally with one card just like any other motherboard.

[guitarwolf]

awesome!!!

thanks!!

[rspassey]

Have you decided on which mobo to go with, I havent had any issues with the Deluxe, except that it would detect my heatsink was running slow at start up, but it was only slow b/c it was not hot and didnt need to run fast.