Ask Dan: Two 7950s or one 8800?

Date: 19 February 2007
Last modified 03-Dec-2011.


I'm in the process of buying a new computer, and I have come to a crossroad with video cards. I cannot determine if I am better off getting 2 Leadtek PX7950GT 512mb cards and running in SLI or getting 1 nVidia 8800GTX 768mb card.

What would your recommendation be? Will I get greater performance in games running 2 cards? Or is it better to just get one top-end card?


Fortunately, the rat's nest that is video card comparisons has become much simpler these days, which makes it very easy for me to answer your question.

No, just kidding. It's as bad as it ever was, if not worse.

Fortunately, it is possible to convey some vague idea of the current state of play without presenting you with 108 graphs of benchmarks from different games at multiple resolutions and with and without different levels of anti-aliasing.

There's no real-world situation I'm aware of in which a single GeForce 8800 GTX will be slower than a pair of GeForce 7950 GTs.

However, there are plenty of situations in which it won't be perceptibly faster, either. Since the price difference is considerable - especially if it turns out that you can make do with a single cheaper video card - it's worth going into more detail.

Here in Australia, an 8800 GTX with 768Mb of memory can be had, as I write this, for $AU946 delivered from m'verygoodfriends at Aus PC Market (Australian shoppers can click here to order one!).

That buys you a Gainward branded card (when I first put this page up there was a slightly cheaper "POV" branded option, but the usual card supplier dance means that's out of stock now...), which is as usual pretty much the same as everybody else's.

512Mb 7950 GTs, on the other hand, can be had for a mere $AU390.50 each, delivered. That's an "Innovision" card, in case you care; it's $AU77 cheaper than the Leadtek you're considering, and I for one would be happy to bet that much money that there's no difference. Aussie shoppers can click here to order one. Or two.

If you're not playing recent card-grinding games at 1600 by 1200 or more with antialiasing turned on, though, you probably don't need even a single 7950 GT.

Let's assume that you've got a recent speedy CPU, so that's not a limiting factor. Let's also set the cut-off point for a smooth and slippery gaming experience at 60 frames per second (when I were a lad, we used t'dream of thirty fps...).

You'll find it difficult to tell the difference between 60fps and higher figures, especially if you've got an LCD monitor, which won't be able to show you more than 60 full frames per second. Yes, there's some small gain to be had from seeing half of one frame and then half of a newer one, but it's not worth big bucks.

Fanatical gamers are also interested in worst-case frame rates, during that one crazy second when everything's happening at once and your frame rate drops, precisely when you most need it to stay high. It's a rare game in which a benchmark average of 60 frames per second doesn't give you a worst-case better than 40 fps, though, and that's still pretty decent. Many benchmarks have less variance than that between the average and the worst-case, because the benchmark itself is ridiculously hectic.

1600 by 1200 with 4X FSAA is not a low output spec. But, for many recent games, you still don't need one of the new shiny video cards to get a solid benchmark average of 60fps at this resolution. Let alone two of them.

In Battlefield 2, for instance, you can very nearly get 60fps at this resolution from a humble 256Mb Radeon X1900 XT. That card's a whole year old now, which of course makes it so ancient and tedious that Aus PC Market don't bother to sell it any more.

A single 7950 GT will do a bit better than this in BF2, getting 65fps or so. SLI-ed 7950s will give you well over 100fps, in case you care.

At even higher resolutions, cards with less than 512Mb of memory can suddenly get considerably slower, as mere frame buffering starts taking up ffity-plus megabytes and cutting into texture and working space storage. But at 1600 by 1200 and below, 256 or 320Mb is still ample.

Still in the not-so-demanding category, Half-Life 2 Episode One will make the 60fps grade with pretty much anything from a Radeon X1950 Pro ($AU300-odd) on up. It is, to be fair, eminently possible to crank Episode One up until a 7950 GT chokes down to thirty-something frames per second. If you insist on doing so, then you'll probably be wanting at least a GeForce 8800 GTS, of which more in a moment. But it's not hard to play an excellent-looking 1600 by 1200 Episode One game with something less expensive.

The more recent Quake 4 is a much heavier load, and it's an OpenGL game and so ought to be faster on the Nvidia cards, because they've been better at that than ATI for years. And this does indeed seem to be the case for the straight timedemo test, especially if you ask for lots of anisotropic filtering and so really push up the RAM demands.

But if you test with a demo that has more going on, and lay off the AF, a mere X1900 XT is apparently still up around 57fps at 1600 by 1200, 4X AA, outperforming more expensive Nvidia cards.

I dunno. Every time you think you've got it straight, someone comes out with another driver version and the goalposts go walkabout yet again.

Anyway, nowadays you're more likely to find the relatively cheap X1950 Pro on sale rather than the X1900 XT, and the 1950 Pro only manages 80 to 90% of the X1900 XT's performance. But for the money, you really can't complain; it's definitely a contender, even for OpenGL.

On the Nvidia side, you'll need at least a single 8800 GTS (the new 320Mb version of which can be yours for $AU517 delivered - Aussies can order that one here) to get more than 60fps in Q4 in intensive play at 1600 by 1200, 4XAA (and it won't be far below 60fps at 1920 by 1200).

A single 8800 GTX is overkill for this, though, floating around in boy racer land above 100fps again pretty much no matter how many monsters jump out of their closets at once.

An X1950 XTX manages more than 60fps in hard testing in Q4 at 1920 by 1440 with 4XAA. It's the thick end of $AU600 delivered, though, so it's not totally thrilling. It's still likely to be better value than dual 7950 GTs for high res Q4, though; the two Nvidia cards will cost you a couple of hundred Australian bucks more, but only squeak in at 60fps-ish at 1920 by 1440 in the same test.

F.E.A.R. is still pretty cruel to video cards at high resolutions and FSAA settings. You'll probably actually need SLI-ed 7950 GTs to stay above 60fps in that at 1600 by 1200, 4XAA. Turn off the FSAA and you can do it with one 7950 GT, though.

For F.E.A.R., a single 8800 GTS squeaks in under our 60fps line, an X1950 XTX is only a few frames per second short of it, and a single 8800 GTX is up around 80fps or something. Which is a nice little buffer to have in case things go really nuts. Which they often do, in F.E.A.R.

Rainbow Six: Vegas is a definite successor to F.E.A.R. in the card-grinding stakes. At 1600 by 1200 with no antialiasing, you're going to need an 8800 GTX or faster to get a reasonably consistent 60fps out of it. Dual 7950s won't cut it there.

And then, yes, there's Oblivion.

Oblivion is so bloomin' tweakable that any definite frame rate figures have to be preceded by a page of detailed video settings, but if you turn on all of the prettiness it will really and truly grind the living heck out of all current PC graphics hardware, even at quite modest resolutions.

On the plus side, Oblivion isn't a twitch game and so the old 30fps standard is quite enough for most people. That's just as well, because the only way to manage 60fps at the moment in Oblivion at 1600 by 1200 with antialiasing (or without it, for that matter) is by using two 8800 GTXs. Fiddle with sliders until the memory load drops a bit, though, and lesser dual-card setups will be fine.

So, obviously, Oblivion really and truly can use everything a single 8800 GTX can deliver. You still won't get much more than 50fps at 1600 by 1200 without antialiasing from a busy high-settings Oblivion scene with one 8800 GTX, though.

A pair of 7950s will give you a playable experience in Oblivion at 1280 by 1024 with high graphics settings but no AA. That'll still only be forty-something frames per second, though.

So, overall:

If your buying decisions are based on the idea that you need more than sixty frames per second in any game, I suggest you discard that idea. 110fps does not look enough better than 60fps to be worth $50, let alone several hundred dollars.

(The only way to properly see more than 60fps is with a CRT monitor. That lowers the bar in another department, though; even if you have a 21 inch CRT monitor, 1600 by 1200 will be a bit fuzzy on it anyway, so high antialiasing levels won't give you anything very noticeable.)

If you're into the latest Rainbow Six or Elder Scrolls games (or Supreme Commander, the retail release of which is just around the corner and will probably bog down our computers just as much as TA did ten years ago), then you really can use 8800 GTX power. And more. And you'll probably be able to use it even if you don't have a 1600-by-1200 or higher monitor.

If you're playing less demanding games, though, bear in mind the basic rule that it's never a good time to buy computer hardware. That goes double for new and shiny graphics cards.

The dual-7950-GT option is not a dumb one, if you've got enough monitor to make high resolutions usable. A single 7950 GT, though, is also a good value card. The 7950 GT is about as much faster as a Radeon X1950 Pro as its extra price justifies, and it rips along very nicely for all sorts of current games at the resolutions that most people can use.

And then, just to make things more complicated, there's that 320Mb 8800 GTS. An SLI pair of those will outdistance an 8800 GTX quite handily, and come close to the performance of twin 8800 GTXs, despite costing only about 1.1 times as much as a single GTX. The smaller amount of RAM on the GTS is the big reason why it's so much cheaper, but only in some games does it have any effect at 1600 by 1200, and even then you can generally dodge the bullet by just turning down the antialiasing and anisotropic filtering a little.

Personally, I think it wouldn't be a bad idea to buy one 7950 GT, or indeed one 8800 GTS, and see how it goes on the games you enjoy. If it's not fast enough, buy another identical one a few days later.

You shouldn't count on a different flavour of 7950 GT (or 8800 GTS) working in SLI mode with your first one - though it is officially supposed to work, with current drivers. You also shouldn't count on a compatible card being available a few months down the track (though, once again, you really ought to be able to pick up another card on eBay and be fine. I don't think Nvidia are offering factory refunds to people who buy two cards of different brands and then find they don't work together, though).

But a given card is not too likely to vanish from the market over the course of a week.

If you just can't live without huge lumps of performance graph passing undigested through your brain, the AnandTech pieces here, here and here will, between them, allow you to build up as coherent a picture of the current state of play as is possible. By the time you've finished flicking browser windows and making spreadsheets, you'll be all ready to go on line and get beaten by someone playing at 640 by 480 with a $3 Xabre card whose defective drivers allow him to see through walls.

Shoppers from Australia and New Zealand can buy graphics cards of all flavours from Aus PC Market. Click here to order!