Big GPU-Shootout; Part III, PCIe 1.0 vs. PCIe 2.0
Conclusion
PCIe 1.0 vs 2.0 performance and 16x+16x Crossfire vs. 16x+4X
Here we have to go back to our ranking to see which of our 5 video configurations benefit best from x48’s doubling of bandwidth over P35’s 1.0 PCI express specification.
- CF-x3
- 4870×2
- 280GTX
- HD4870-1GB
- HD4870-512MB
Upgrading crossfire-ready motherboards with a second graphics card is an excellent way for gamers to generally extend the useful life of their systems as it provides good performance increases at medium to high resolutions, with high details and especially with 4xAA/16xAF. Our individual benchmarks show that crossfireX-3 performance is rather inconsistent on P35 motherboards. We saw occasionally how one could suffer losses due to the low bandwidth of the second graphics card slot. If you have a P35 motherboard you might want to consider which games you will be playing before buying that second video card.
The easy solution for P35 express systems is to simply use a single, more powerful card. Where a secondary PCI Express x4 slot’s limited bandwidth might hurt performance, it best avoided by using a single powerful card. Of course, GTX280 or crossfire sandwich cards like 4870-X2 are also held back a bit by P35MB’s PCIe 1.0 compared to X48’s PCIe 2.0 bandwidth. However, in judging the usefulness of adding a second card when a powerful card is already installed, we can see that P35 express motherboards simply cannot be upgraded as well as X48.
Now when we are speaking 4870-512MB vs. 4870-1GB, it is likely that the 1GB card will have an advantage going forward for new games. Larger textures are always coming out and the 1GB version might be a good “investment” if you are planning to keep your card a couple of years. Our 4870-512MB just falls short of the 1GB version for maximum detailing and/or added AA/AF, yet both would be excellent for playing the newest and most demanding PC games at 1680×1050. We also saw the immaturity of the Crossfire-X3 drivers holding back performance of “true crossfire” – 4870-X2 plus 4870-1GB – over the “frankenfire” 4870-X2 plus 512MB 4870. It appears from our testing that 512MB VRAM limitations using 4870-512MB paired with 4870X2-2GB in crossfireX-3 exist for specific games and/or settings even including 1680×1050 resolutions. Especially in the upcoming DX10 PT Boats, 512MB VRAM would be a real disadvantage. CrossfireX-3 is a little faster than 4870-X2 and is becoming less and less of a curiosity than with previous drivers and it also stands to benefit most from PCIE 2.0 over 1.0 with improving drivers. We expect the situation will continue to improve as we are continuing our testing with Catalyst 8-12 now for future articles in our series.
We definitely see that our new X48 motherboard’s PCIe 2.0 specification makes some solid differences performance-wise over our PCIe 1.0 P-35 motherboard but it clearly depends on which card is used and what game is played. PCIe express 2.0 is not so critical for 4870-512MB class video cards but becomes more increasingly noticeable with GTX280 and 4870-X2 – and especially crossfire-X3 – when it scales well.
We will be back very soon with Part IV of our testing – using Catalyst 8-10 and Geforce 178.24 in a short article to get up to date, quickly and then Cat 8-11 compared with 8-12 and Geforce 180.48. Over this series, we also watch Nvidia’s drivers evolve over the same period as AMD’s to see if they managed to get more performance out of their Tesla architecture. We also expect to explore Nvidia’s propriatory PhysX with their Big Bang Drivers II (180.48) vs. Catalyst 8-12 and ATi’s now-enabled “Stream” drivers which is meant to take on Nvidia’s CUDA.
Here is our planned “GPU-Shootout” series:
Part I – Cat 8.8 (8/20/08) vs Geforce 177.41 (06/26/08) (p35 MB platform)[done]
Part II – Cat 8.9 (9/17/08) vs Geforce 178.13 (09/25/08) (p35 MB platform)[done]
Part III – Cat 8.9 (9/17/08) vs Geforce 178.13(09/25/08) (x48 MB platform from now on)[Done]
Part IV – Cat 8.10 (10/11/08) vs Geforce 178.24 (10/15/08) [benches completed]
Part V – Cat 8.11 (11/13/08) and Cat 8.12 (12/12/08) vs. Geforce 180.48 (11/19/08)
(Stream vs BigBangII; benching in progress)
– in the meantime, please check out Leon’s excellent mini Cat 8-11 vs 8-12 performance review with 4870 here.
We also just got our hands on a brand New DX10 Benchmark from STALKER, Clear Sky! .. it is “official” and was released at the very end of last year. It is our very next article – due tomorrow! And we will check it with the very latest drivers and we will add 12×10 resolution as we will also intend to show last generation’s 8800GTX and 2900xt benchmarks also. In a couple of weeks, we expect to also have Intel’s new 65w, low-power QuadCore Q9550 in for testing and we will also give you stock and overclocked comparisons of it vs. our Core2Duo e8600 which we can now get to well over 4.0Ghz.
–After that, we expect to compare the maturing Intel Core i-7 CPU platform with our current maxed out Penryn system … and we expect to also explore Nvidia GTX280/290 SLi on an X58 motherboard.
Stay tuned. All four parts of our planned testing has been completed – with Part V testing in progress – and we think we will have some very interesting articles for you to read very shortly as you plan your own coming upgrades.
Mark Poppin
ABT Editor
Curious, why’d you set Catalyst A.I. to “Advanced”?
How about a few links to explanations of Catalyst AI and what “advanced” really does? Here is an old article on it:
http://www.hardocp.com/article.html?art=NjY2LDI=
Here is the tweak guide which supports my own research:
http://www.tweakguides.com/ATICAT_7.html
“Catalyst A.I. allows users to determine the level of ‘optimizations’ the drivers enable in graphics applications. These optimizations are graphics ‘short cuts’ which the Catalyst A.I. calculates to attempt to improve the performance of 3D games without any noticeable reduction in image quality. In the past there has been a great deal of controversy about ‘hidden optimizations’, where both Nvidia and ATI were accused of cutting corners, reducing image quality in subtle ways by reducing image precision for example, simply to get higher scores in synthetic benchmarks like 3DMark. In response to this, both ATI and Nvidia have made the process transparent to a great extent. You can select whether you want to enable or disable Catalyst A.I. for a further potential performance boost in return for possibly a slight reduction in image quality in some cases. If Catalyst AI is enabled, you can also choose the aggressiveness of such optimizations, either Standard or Advanced on the slider. The Advanced setting ensures maximum performance, and usually results in no problems or any noticeable image quality reduction. If on the other hand you want to always ensure the highest possible image quality at all costs, disable Catalyst A.I. (tick the ‘Disable Catalyst A.I.’ box). I recommend leaving Catalyst A.I enabled unless you experience problems. ATI have made it clear that many application-specific optimizations for recent games such as Oblivion are dependent on Catalyst AI being enabled.
Note: As of the 6.7 Catalysts, Crossfire users should set Catalyst A.I. to Advanced to force Alternate Frame Rendering (AFR) mode in all Direct3D games for optimal performance. Once again, Catalyst A.I. should only be disabled for troubleshooting purposes, such as if you notice image corruption in particular games”
In other words, one can choose the aggressiveness of your optimizations, either “Standard” or “Advanced”. The Advanced setting ensures maximum performance – as for benchmarking games – and with no noticeable image quality reduction. However, if you are doing IQ comparisons as BFG10K did, and want to guarantee the very highest image quality, then disable Catalyst A.I. [but not for crossfire; set it to “Standard”]. I have always recommended leaving Catalyst A.I enabled unless you experience any glitches in games.
You have to realize that Cat AI is not necessarily supposed to give you a boost in every single game. It tries to do optimizations, if possible, but many times these are either not possible with a particular game, or the settings you’ve chosen in the game may be too low for it to make any noticeable impact.
That is why I recommend leaving it on “Advanced”; you get a possisble performance boost; if not then you lose nothing. Or you can set it to standard or off if you feel your image quality is being degraded.
Hope that explains it.
Very interesting, I’ll definitely be I check your site on a regular basis now.