by Alexey Stepin
07/15/2005 | 12:35 PM
Besides the obvious advantages described in our review, NVIDIA’s SLI technology also has some unpleasant restrictions. One of them is you cannot join two GeForce 6800/6600 graphics cards into a SLI pair if the cards are not identical models made by the same manufacturer. It is as yet impossible to make a SLI configuration on GeForce 6600 GT or 6800 GT/Ultra out of graphics cards of different brands, even if their technical characteristics coincide.
<%BANNER[article]%>This fact was proved in our tests, too. You may meet a serious compatibility problem if you’re willing to buy a single GeForce 6600 GT or 6800 GT/Ultra today and then upgrade this graphics subsystem with a second such card. In fact, there may be problems even if the second card is from the same manufacturer. The newer card may have a different BIOS, and not all people would dare experiment and reflash it.
NVIDIA, on its part, promises to correct this drawback in near future, thus giving the user more flexibility in applying the multi-GPU solution.
Another thing to be mentioned is that the GeForce 6800 Ultra PCI Express is still a relatively rare and expensive device, even after the recent release of the GeForce 7800 GTX. No wonder then that there have begun to appear special kits consisting of two graphics cards on NVIDIA GeForce 6600 GT GPUs that are guaranteed to be SLI-compatible. We received one such kit from Leadtek whose produce has been repeatedly tested and reviewed in our labs.
So today we’re going to talk about the WinFast PX6600 GT TDH SLI kit from Leadtek.
The brown-colored package looks exactly like the box of the single Leadtek WinFast PX6600 GT TDH.
There’s no mention anywhere that this is a kit of two graphics cards. The NVIDIA SLI label was present on the box with a single WinFast PX6600 GT TDH, too. Leadtek decided just to double the accessories, so besides the two WinFast PX6600 GT TDH graphics cards we have all things in pairs here:
We already wrote about the advantages of the universal video splitter from Leadtek in our review called Leadtek WinFast PX6600 GT TDH Graphics Card Review – it is easier to connect to various display devices like TV-sets, projectors and plasma panels with this splitter than with ordinary adapters. The accessories are sufficient. You receive everything necessary to successfully install and use the Leadtek WinFast PX6600 GT TDH SLI kit.
A SLI adapter that would connect the two cards is missing among the accessories, and for good reason. The fact is different models of SLI-compatible mainboards have the PCI Express x16 slots at a different distance from each other, so there just can’t be a universal SLI adapter suitable for all mainboards. For example, an adapter that suits the ASUS A8N-SLI will not work on the MSI K8N Diamond just because the PCI Express x16 slots are much closer to each other on the latter mainboard. So, it is the mainboard that must include a SLI adapter as an accessory rather than the graphics card, and there’s nothing wrong that the Leadtek kit doesn’t has one.
Leadtek’s multi-GPU kit includes two WinFast PX6600 GT TDH graphics cards that don’t differ from the standalone card we described in our review called Leadtek WinFast PX6600 GT TDH Graphics Card Review.
The cards are equipped with simple, quiet but efficient coolers, so they produce rather little noise even working together. So, the acoustic characteristics of Leadtek’s kit will be quite acceptable even for fastidious users.
As for the installation process, we had no problems whatsoever: the cards are very small and, unlike GeForce 6800 Ultra, do not block the PCI Express x1 slots and the latches of the PCI Express x16 slots. In our case, both PCI Express x1 slots remained available, although we wouldn’t recommend you to install a long card into the top one lest it should cut off the cooler of the top graphics card. On the other hand, PCI Express x1 devices are still very rare, so you’re unlikely to find yourself lacking the appropriate slots on the mainboard.
The distance between the installed cards is long enough for normal circulation of air inside the system case. There should be no problems about cooling the two WinFast PX6600 GT TDH cards even on mainboards where the PCI Express x16 slots are closer to each other. Another nice thing is that you don’t have to attach additional power and thus you can avoid the mess of cables you usually have with top-end graphics cards.
Mainstream graphics cards from Leadtek had already got our praises for their very quiet operation and we had expected the SLI kit to be quiet enough, too. And we were not mistaken: the two PX6600 GT TDH cards were not much louder than the single card and their noise wasn’t annoying at all against the noise from the rest of the system components. So, if you care about your hearing, this kit should please you.
Using the new version of the ForceWare driver we managed to overclock the kit without third-party utilities. The results were not much of a success, though. We only got a 45MHz GPU frequency gain and a 10 (20DDR) MHz memory frequency gain. In other words, the Leadtek WinFast PX6600 GT SLI was stable at 545/510 (1020DDR) MHz frequencies. Our trying to overclock the kit more resulted in various image artifacts in games. So, this can hardly be called successful overclocking, especially since some samples of the GeForce 6600 GT can speed up to 600/550 (1100) MHz, but we deal with a SLI kit here and this fact may have brought some limitations.
The quality of the 2D image was very high, quite typically for a modern graphics solution. Installed into the master PCI Express x16 slot, both cards produced an excellent-quality picture in all display modes, up to our Dell P1110’s maximum of 1800x1440@75Hz.
So, the Leadtek WinFast PX6600 GT SLI kit is easy to install and quiet in operation. The only thing we now want to find out about this kit is if the speed of this solution can match the speed of such single top-end cards as RADEON X850 XT and GeForce 6800 Ultra.
We tested Leadtek’s SLI kit on the following testbed:
Software:
Besides the WinFast PX6600 GT TDH cards from the Leadtek kit, we also tested the following graphics cards:
Following our traditional methodology, we enabled the ForceWare optimizations, except the Anisotropic mip filter optimization. The Image settings slider was set to the Quality position. In ATI’s Catalyst we enabled Catalyst A.I. using the Standard mode. The Mipmap Detail Level option was set to Quality.
If possible, we control FSAA and anisotropic filtering from the application. Otherwise, we force the necessary mode from the driver. We don’t edit any configuration files. The graphics quality settings in the games were set to the maximum level, the same for graphics cards from NVIDIA and ATI Technologies. The following games and applications were used:
First Person 3D Shooters:
Third Person 3D Shooters:
Simulators:
Strategies:
Semi-Synthetic Benchmarks
Synthetic Benchmarks
The Leadtek kit performs on the same level as the GeForce 6800 GT in this game and is a little slower than the GeForce 6800 Ultra. Note that there’s almost a zero effect from overclocking – a speed gain of 1-2fps is really negligible.
It’s different when we enable such picture-enhancing options as full-screen anti-aliasing and anisotropic filtering. The combined amount of graphics memory of the WinFast PX6600 GT TDH kit is only 128MB and it cannot rival the GeForce 6800 GT that has 256 megabytes of memory on board. Even though the Leadtek solution delivers the performance of an ATI RADEON X850 XT Platinum Edition, we can’t call this a good result since ATI’s cards are generally slower in Doom 3 than their NVIDIA counterparts due to the specifics of the game engine and ATI’s less efficient OpenGL driver. Moreover, a speed of 25-30fps isn’t enough for comfortable play.
The Leadtek kit even outperforms the GeForce 6800 Ultra on the d3dm4 map, probably because this multiplayer map is simpler, having no game characters. Overclocking is unrewarding, again.
Having a small amount of memory and two 128-bit buses instead of a single 256-bit one, the WinFast PX6600 GT TDH SLI is ahead of the GeForce 6800 GT in the lowest resolution only. In higher resolutions it slows down and is just about 10% faster than the RADEON X800 XL in 1600x1200.
The graphics cards all have the same “pure speed”. This is normal because Unreal Tournament 2004 isn’t anything too difficult for modern graphics processors.
The results observed in the “eye candy” mode show that one and one isn’t necessarily two when it comes to multi-GPU technologies. The performance of the Leadtek kit equals that of the single GeForce 6600 GT, meaning that SLI technology doesn’t work here even with the new version of ForceWare.
The gaps between the participating cards can be seen more clearly on the Metallurgy map. The Leadtek kit is slower than the rest of the participating cards in 1600x1200.
Like in the previous case, NVIDIA’s SLI works incorrectly in Unreal Tournament 2004 . The speed of the Leadtek WinFast PX6600 GT TDH SLI equals the speed of the single PX6600 GT.
We couldn’t enable the multi-GPU mode in the Chronicle of Riddick even using the new ForceWare. The performance of the WinFast PX6600 GT always remained on the level of the single GeForce 6600 GT, with a comfortable frame rate in the two lower resolutions only.
It’s the same in the “eye candy” mode. Since only one card was actually working, no wonder the performance of the Leadtek kit was below that of the RADEON X800 XL in this shooter. The SLI platform doesn’t ensure playability when full-screen anti-aliasing and anisotropic filtering are enabled in this game.
The Leadtek kit isn’t any worse than the GeForce 6800 GT on the open and water-abounding Pier level. The GeForce 6800 Ultra is faster, though, not to mention the RADEON X850 XT Platinum Edition with its highest pixel shader performance. Overclocking brings no positive effects to the SLI platform.
We again see the Leadtek kit lacking more graphics memory and more memory bandwidth in the FSAA + AF mode. The SLI platform performs worse than the GeForce 6800 GT and its efficiency is diminishing in higher resolutions. In 1600x1200 the gap between it and the GeForce 6800 GT is as big as 25% and the performance of the Leadtek kit is unacceptably low.
The second Far Cry map we use in our tests of graphics cards depicts a cave lit with per-pixel light sources. The Leadtek kit is even a little ahead of the GeForce 6800 GT in high resolutions: the memory load is lower here, while the pixel shader performance is more important. The WinFast PX6600 GT TDH has a higher GPU clock rate and thus a higher pixel shader performance than the GeForce 6800 GT does. Yet anyway, the RADEON X850 XT PE remained an unrivalled leader here, too.
Unlike on the Pier map, the lack of memory bandwidth is felt only in 1600x1200. Up to this resolution the two WinFast PX6600 GT cards are at least as fast as the GeForce 6800 GT.
The speed of Painkiller depends heavily on the frequency of the graphics processors. Looks like a good environment for the SLI kit from Leadtek? Not quite. It is noticeably slower than the GeForce 6800 GT, not to mention the GeForce 6800 Ultra. The gap is about 10-12%.
It’s different in the “eye candy” mode: the SLI platform is still slower than the GeForce 6800 GT but the gap is getting narrower in higher resolutions. The WinFast PX6600 GT TDH SLI is already faster in 1280x1024 and comes even with the GeForce 6800 Ultra in 1600x1200. The RADEON X850 XT Platinum Edition is an unrivalled leader, though.
The Leadtek kit isn’t much slower than the GeForce 6800 GT in Half-Life 2 . The gap is only 3-6fps, the absolute frame rates being about 100fps. There’s a lot of water on this level, so ATI’s cards – from the RADEON X800 XL to the RADEON X850 XT Platinum Edition – are victorious in this test.
When we enable full-screen anti-aliasing and anisotropic filtering, the graphics cards with NVIDIA’s GPUs suddenly go ahead in resolutions of 1280x1024 and higher. But the Leadtek WinFast PX6600 GT TDH SLI again suffers from the lack of graphics memory, being up to 30% slower than the GeForce 6800 GT. Anyway, the SLI platform ensures playability in all the tested resolutions.
The scene recorded on the d3_c17_02 map is very CPU-dependent, as it shows a fight of Gordon Freeman accompanied by a robot with patrol soldiers. The results on this level are very similar between the cards: only the ATI RADEONs are prominent among the others.
The Leadtek kit suffers from the inherent disadvantages of SLI technology immediately: its performance falls to below the level of the GeForce 6800 GT in 1024x768, and 1600x1200 resolution is not playable – 30fps is too little for a 3D shooter.
Splinter Cell: Pandora Tomorrow was the first game where overclocking gave some speed bonus to the WinFast PX6600 GT TDH kit. Yet even this didn’t help it to get to the level of the GeForce 6800 GT. The resolutions up to 1280x1024 are only playable. We want to remind you that we benchmark third-person shooters with a third-party utility and the results should be regarded as approximations.
Overclocking brings in a rather high speed gain in Prince of Persia , too. The Leadtek solution is about 5-15% slower than the GeForce 6800 GT at the default frequencies and only 2-5% slower at the overclocked frequencies (545/1020MHz). The overclocked Leadtek SLI platform is even as fast as the GeForce 6800 Ultra in lower resolutions. Still, the RADEON X800 XL looks preferable, even in high display modes.
The results suggest that NVIDIA’s multi-GPU technology works incorrectly with ForceWare 71.89. The two Leadtek WinFast PX6600 GT TDH cards have almost the same speed as the single device.
It’s the same in the “eye candy” mode. Unfortunately, we couldn’t make SLI work in this popular flight simulator.
In Lock On , however, SLI shows its best, and the Leadtek kit is just a little behind the GeForce 6800 GT. Alas, the game is so hungry for resources at the maximum graphics quality settings that even 1024x768 resolution is hardly playable.
The SLI platform is worse than the top-end single cards in the “eye candy” mode, starting from 1280x1024 resolution. It is as far as 30-35% behind the GeForce 6800 GT in 1600x1200. The benchmarking results in Lock On should also be regarded as approximations since this game doesn’t have built-in benchmarking tools.
Colin McRae Rally 2005 makes extensive use of pixel shaders, whose speed directly depends on the GPU frequency. This fact explains the results the Leadtek WinFast PX6600 GT TDH SLI shows in this game. Although the SLI platform is comparable to the ATI RADEON family only in 1024x768, it is always faster than the GeForce 6800 Ultra. We also enjoyed a noticeable bonus from overclocking the Leadtek kit here: about 10%.
Despite some architectural flaws, the dual-Leadtek kit outperformed GeForce 6800 Ultra in the first two resolutions and ran neck and neck with it in 1600x1200. Anyway, the winner’s laurels remained by ATI RADEON graphics cards, which proved faster when processing pixel shaders.
The performance of a GeForce 6800 Ultra or a RADEON X850 XT Platinum Edition is what the Leadtek SLI kit can offer to the strategic mind, particularly in the relatively new title Warhammer 40K: Dawn of War .
The SLI platform performs somewhat worse in the FSAA + AF mode, yet it matches the GeForce 6800 GT and – at the overclocked frequencies – the RADEON X850 XT PE. It is only in 1600x1200 resolution that the small amount of memory hamstrings the WinFast PX6600 GT TDH duo and the SLI platform only competes with the RADEON X800 XL. On the other hand, this is not that important since all the participating cards, except the GeForce 6800 Ultra, are too slow for comfortable play in this resolution.
This is the most demanding strategy game we’ve ever seen. Even the best graphics cards can seldom score more than 30-35fps in it, and the Leadtek kit is among them. It has the same speed as the GeForce 6800 GT or the RADEON X850 XT have. The GeForce 6800 GT slows down in 1600x1200, and the Leadtek solution challenges the GeForce 6800 Ultra in this resolution. When overclocked, the SLI platform is on the same level of performance as the RADEON X850 XT Platinum Edition, the fastest single graphics card participating in this review.
The results of the “eye candy” mode clearly show that the graphics memory bandwidth isn’t a crucial factor for Perimeter . The Leadtek kit has the best result, especially in higher resolutions. It is simply unrivalled at the overclocked frequencies. By the way, a frame rate of 30fps is quite enough for this game – it is a comfortable and playable speed.
SLI technology does not work in this test. The Leadtek multi-GPU kit is slower than the single card.
NVIDIA’s SLI not just works in Aquamark , but is highly efficient: the Leadtek WinFast PX6600 GT TDH SLI kit goes abreast to the RADEON X850 XT Platinum Edition. This test is free from complex shaders, so our overclocking the SLI platform yields almost no perceptible gain.
Up to 1600x1200 resolution the SLI kit from Leadtek performs just like the RADEON X850 XT, but the small amount of memory and the narrow 128-bit memory buses restrain its performance in the highest display mode. And still, even in this case the Leadtek kit successfully competes with the RADEON X800 XL that is equipped with a more advanced memory controller.
The Leadtek has an excellent general result in 3Dmark03, but this benchmark defaults to 1024x768 resolution were the graphics memory subsystem has the least influence on the results. So, we must examine the results of each of the subtest independently to see if this high overall score is well deserved.
The two WinFast PX6600 GT TDH cards aren’t too fast in the first and simplest test, especially in lower resolutions. The SLI platform is slower than the GeForce 6800 GT and the RADEON X850 XT Platinum Edition. Overclocking raises the Leadtek kit to the level of the GeForce 6800 Ultra.
Leadtek’s SLI solution is successfully competing with the GeForce 6800 Ultra after we have enabled full-screen anti-aliasing and anisotropic filtering. In 1600x1200, however, its performance goes down to the level of the GeForce 6800 GT. Based on an older version of DirectX, the first test isn’t descriptive of the capabilities of modern graphics cards. Let’s see what we have in more difficult tests.
The second test can make use of the architectural features of the NV4x family processors. Coupled with the high frequencies of the Leadtek kit, the SLI platform leaves even the GeForce 6800 Ultra behind.
It can’t retain this position for long in the “eye candy” mode, however. The lack of memory and the smaller efficiency of the two 128-buses affect the performance of the SLI platform negatively in resolutions above 1024x768. Overclocking is almost of zero effect here since it is the memory frequency that’s important for doing full-screen anti-aliasing and anisotropic filtering, and we raised this frequency by very little.
The results of the third test generally repeat those of the second one, with Leadtek’s SLI kit on top, because these two tests differ in the plot but are technologically very much like each other.
Again like in the second test, Leadtek’s SLI system is the best in the lowest resolution, but then come abreast to the GeForce 6800 Ultra.
The speed of the fourth game test depends mostly on the speed of execution of version 2.0 pixel shaders. Clocked at 500MHz each, the two graphics processors from the Leadtek kit deliver the performance of an ATI RADEON X850 XT Platinum Edition. Moreover, overclocking them to 545MHz makes the Leadtek SLI kit the winner in this test. The performance gain from overclocking is 5-8%.
Like in the two previous tests, the Leadtek kit is a leader in 1024x768, but loses its first place to ATI’s cards which are equipped with the most advanced memory controller for today. So, the high overall 3DMark03 score of the Leadtek WinFast PX6600 GT TDH SLI is only correct in the “pure speed” mode. With enabled full-screen anti-aliasing and anisotropic filtering, however, the SLI platform performs much like a GeForce 6800 Ultra or a RADEON X850 XT Platinum Edition.
The Leadtek kit is only 155 points worse than the RADEON X850 XT Platinum Edition and beats it at the overclocked frequencies. Let’s see what we have in the subtests.
Outperforming the GeForce 6800 Ultra and going almost at the same speed with the RADEON X850 XT in the first two resolutions, the SLI platform can only do the same through overclocking in 1600x1200. Overclocking is really rewarding here, ensuring a 10-20% performance gain.
The new driver helped us launch this test on NVIDIA’s graphics cards equipped with 128MB of memory in 1280x1024 resolution of the “eye candy” mode (earlier, only 1024x768 had been available). In the lowest resolution the Leadtek kit isn’t much worse than the GeForce 6800 Ultra, but slows down below the level of the GeForce 6800 GT in 1280x1024 – 3DMark05’s scenes feature highly complex graphics, and the amount and bandwidth of the graphics memory play a crucial role in the “eye candy” mode.
The Leadtek SLI platform shows its best in the second test, being at least no slower than the RADEON X850 XT Platinum Edition. It is sad 3DMark is just a synthetic test rather than a real game, but anyway the fact is the two Leadtek WinFast PX6600 GT TDH cards are faster here than top-end single-GPU solutions.
There’s an astonishing 30% speed bonus overclocking gives you in the “eye candy” mode. Well, the Leadtek kit is as fast as the GeForce 6800 GT even at its default frequencies. As for 1280x1024 resolution, the non-overclocked Leadtek solution competes with the GeForce 6800 Ultra there.
The third test is the most difficult one, containing numerous sophisticated pixel shaders. Yet even here the SLI platform competes with the RADEON X850 XT Platinum Edition in two resolutions out of three. Unlike in the first two tests, overclocking is of no effect almost.
Leadtek’s SLI solution isn’t disappointing in the “eye candy” mode, either. Outperforming the GeForce 6800 GT, it is even with the RADEON X800 XL in 1024x768 and slightly behind it in 1280x1024. Like in 3DMark03, the high overall result of Leadtek’s SLI kit is fully confirmed in each subtest.
Leadtek’s WinFast PX6600 GT TDH SLI kit consists of two WinFast PX6600 GT TDH graphics cards which are identical to the standalone card we described in a separate review. And these two cards too deserve our praises for their quiet and efficient cooling system, good accessories and high image quality.
But when it comes to performance, the results of our today’s tests once again prove that NVIDIA’s SLI technology is not appropriate for mainstream graphics cards. The Leadtek kit is really good in some tests, but is slower than the GeForce 6800 Ultra/GT and RADEON X850 XT in others, especially when you enable full-screen anti-aliasing and anisotropic filtering. The reasons are obvious: the small amount of graphics memory (only 128 megabytes) and the lower efficiency of the two 128-bit memory buses against the single 256-bit bus of the GeForce 6800 Ultra/GT and RADEON X850 XT.
Beside the high price on the SLI kit proper, the multi-GPU technology also requires a not-very-cheap SLI-ready mainboard with two PCI Express x16 slots. Of course, buying a Leadtek SLI kit, you are guaranteed to have no compatibility problems, but you will be limited with 128 megabytes of graphics memory (this is already not enough for many latest games), while the performance in high resolutions will often be less than that of a single top-end graphics card. Yes, you can play in low resolutions and without full-screen anti-aliasing, but it would make no sense – why pay more if you still cannot use the quality-enhancing features and play with comfort?
Yet another problem with SLI is that you don’t get a performance gain from adding a second card in some games, while a GeForce 6800 GT or a RADEON X800 XL will always give you their maximum performance. The stability of the dual-chip solution is also lower than that of the single-chip card – you may have image artifacts in some games with certain driver versions in the multi-GPU mode.
That said, we do not recommend you to buy a multi-GPU SLI kit consisting of two GeForce 6600 GT cards. We think a single GeForce 6800 GT or Ultra or RADEON X850 XT/RADEON X800 XL will be a better choice since these cards will let you enjoy comfortable and trouble-free play even with enabled full-screen anti-aliasing and anisotropic filtering.
Highs:
Lows: