AGP vs PCIe performances

The different performances of the two interfaces

It’s a fact that the PCI Express bus offers higher performances than the AGP. However, in practice what does this actually mean in games. To answer this question, we tested a GeForce 7600 GT and Radeon X1950 Pro in their AGP and PCI Express versions.





Differences were nevertheless minimal, and we can’t really say that a more recent graphic card will be restrained by an AGP bus even if its performances are generally 2-3% lower.

The older generations

The older generations

As a reference and to allow you to better judge the performances of recent AGP cards compared to your current hardware, we included some of the older generation : the GeForce FX 5900XT, 6800 GT and 6600 GT, as well as the Radeon 9800 Pro and X800 XT PE.

GeForce FX 5900XT

The very criticized GeForce FX line is still found in a number of PCs. Its architecture is poorly adapted to DirectX 9, and it should have significant problems with some of the more recent games. Indeed, some of Nvidia’s specific optimizations hinted at this and evidence showed that these cards were especially intended for DirectX 8, even though complete DirectX 9 support was available.




The GeForce FX 5900XT manages AGP natively and is equipped with 128 MB of 256 bit memory. It needs a supplementary molex power supply.

GeForce 6800 GT

The high end of the GeForce 6 line, the GeForce 6800 GT was very successful and offered good performances thanks to its revised architecture and Shader Model 3.0 support.




AGP is also native with this card. The GeForce 6800 GT is equipped with 256 Mo of memory linked to 256 bit bus. A molex power supply is also required.

GeForce 6600 GT

The GeForce 6600 GT was very successful and was sold in large volume. There are numerous users of this card, which represents a sort of reference for mid-level performances.




The GeForce 6600 GT was the first Nvidia GPU to manage Nvidia PCI Express natively. A bridge, called the HSI, was thus present on the AGP version, serving as an intermediary between the PCI Express and AGP interfaces. This card has 128 MB in 128 bits. Although there are 256 MB versions, the 128 MB is the most representative of its class.

Radeon 9800 Pro

A boosted version of the Radeon 9700 Pro, the 9800 Pro was a success. The first to feature DirectX 9 architecture, its implementation was very effective from the start. Even if we had to wait for the inefficiency of the GeForce FX to be confirmed for it to finally be given the merit it was due, this card was very popular. Five years later, how does this architecture fare?




The Radeon 9800 Pro manages AGP natively and has 128 Mo of memory with a 256 bit interface. A supplementary power connection of floppy disc type is necessary.

Radeon X800 XT PE

An evolution of previous Radeons, the X800 has twice the number of processing units and supports an extended version of Shader 2.0 (with Pixel Shader 2.0b), which allowed it to bypass some limitations. ATI thus focused on processing power, while Nvidia opted for a less powerful but more evolved architecture with the GeForce 6.




The card manages AGP natively and is equipped with 256 MB of memory in 256 bit. A molex connector is required.

The new generation

The new generation

GeForce 7600 GT Leadtek

The WinFast A7600 GT TDH was built on the reference design of the GeForce 6600 GT AGP.


This card is equipped with 256 MB of memory and needs an additional molex power supply. It comes with PowerDVD, SpellForce 2, Trackmania Nations, a DVI/VGA adaptor and an HDTV cable.

GeForce 7800 GS Point of View

The GeForce 7800 GS is (contrary to what its name may imply) a G71 or GeForce 7900. It has, however, two-thirds the calculation units set at a lower frequency. Although, based on the same chip as the GeForce 7900 GTX, its calculation power is 2.5 times inferior. This makes us question the interest of this card in relation to the GeForce 7600 GT, something we will verify.



The card is equipped with 256 MB and needs a molex connector. The package includes Dark Messiah Might and Magic, Prince of Persia The Two Thrones, Hitman Blood Money, a molex connector, DVI/VGA adaptor, an HDTV cable and a T-Shirt.

Radeon X1650 Pro Sapphire

This mid-level card really didn’t attract the same enthusiasm, with which it was launched. The Radeon X1650 Pro now represents the entry level of the Radeon X1000 line.




This card is equipped with 256 Mo in 128 bits and needs a supplementary power connection of the disk drive type. It comes with a power cord, composite/S-video adaptor, S-video cable, HDTC cable and a DVI/VGA adaptor. Note that the cooling system is a double slot, something we find unjustified for this type of card.

Radeon X1650 XT PowerColor

Based on a lesser version of the X1950 Pro, the Radeon X1650 XT finally represents an interesting mid-level ATI card.



It has 256 MB of memory in 128 bits and needs a PCI Express power connection. It comes with Cyberlink DVD Solutions, a molex/PCIE power cable, composite/S-video and DVI/VGA adaptors. The cooling system is a double slot but is relatively quiet.

Radeon X1950 Pro PowerColor

Besides the Radeon X1950 XT, which is specific to Gecube, the Radeon X1950 Pro is the most powerful in AGP.



The card has 256 MB (also exists in a 512 MB version) and needs a PCI Express power connection. It comes with Cyberlink DVD Solutions, molex/PCIE power, composite/S-video and HDTV cables, and a DVI/VGA adaptor. PowerColor chose Artic Cooling, which is imposing but also efficient and silent.

Specifications, the Vista test

Specifications

In this table you will find a summary of specifications of all the different cards in this test:

You may have noticed that despite its name, a GeForce 7800 GS is actually (except in memory bandwidth) inferior to a GeForce 7600 GT.

Windows Vista

We tested how each card functions with the Aero interface of Windows Vista. There were no problems except for the fact that Nvidia didn’t update the drivers for the GeForce FX.

The tests

For this test there were five games: Quake 4, Half-Life 2, Rainbow Six Vegas, Oblivion and Need for Speed Carbon. Given that these are former and recent mid-level cards, we opted for resolutions of 1024x768 and 1280x1024 and anisotropic 4x filtering (except for Quake 4, which automatically activates 8x). We also tested performances in video decoding. The CPU, an Athlon 64 3700+, is a good platform for AGP. It isn’t an extreme CPU, which isn’t representative of an AGP system to be updated.

Test configuration:

Athlon 64 3700+
MSI K8N Neo2
2x 512 MB DDR
Windows XP SP2
ForceWare 93.71
Catalyst 7.2

Quake 4

Quake 4

Here, we saved an action scene. Unlike Doom 3, there are fewer shadows and more characters and textures. This changes the load in terms of rendering.

Anisotropic filtering 8x was automatically activated by the game and the test was carried out in high quality mode.




The high end solutions were CPU limited. The 7600 GS was ahead of the X1650 Pro and GeForce FX couldn’t overtake the 9800 Pro.

Once antialiasing was activated, the Radeon X1950 Pro gained the lead, followed by the Radeon X800 XT PE, which overtook the GeForce 7800 GS, 7600 GT and 6800 GT. The X1650 Pro was ahead of the 7600 GS, and gaming wasn’t possible with the 9800 Pro and FX 5900 XT in these conditions.

Half-Life 2 Lost Coast

Half-Life 2 Lost Coast

For this test, we use an internal demo recorded with Lost Coast to test Valve's HDR, which uses a quite complex rendering format. It doesn’t maximize the additional capabilities of the GeForce 6, 7 and Radeon X1K, but runs with all DirectX 9 cards with MSAA.

4x anisotropic filtering was activated via the game. The GeForce FX do not officially support DirectX 9, as they were considered too poor in this domain. Therefore, rendering is simplified and is carried out in DirectX 8. You can force DirectX 9, but performances collapse and there are too many bugs (for example, water isn’t displayed).




Despite the DirectX 8, the GeForce FX still finish last.



The Radeon X1950 Pro takes the lead and the GeForce 7800 GS and 7600 GT tie.


Because HDR mode isn’t available in DirectX 8, the GeForce FX can’t use it. The Radeon X800 XT PE nevertheless manages to finish before the Radeon X1650 XT, GeForce 7600 GT and 7800 GS.

Oblivion

Oblivion

We saved a specific movement that could be reproducible and always identical for this test.

4x anisotropic filtering was activated via drivers.




The Radeon seemed to be at ease with Oblivion and clearly dominate. The GeForce FX are behind and aren’t too sure what to make of DirectX 9 games. Note that there was a bug in Nvidia rendering and some textures were pixellated with GeForce 7 and 6 (probably the specular effect). Finally, the quality of the Radeon 9800 Pro and GeForce FX 5900 XT is slightly less, because they can’t display high quality shadows. Developers, however implemented this mode in Pixel Shader 2.0b so that it could function with the Radeon X800 XT PE.


With antialiasing, ATI slightly widens the lead. The Radeon X800 XT PE once again comes out rather well, while the GeForce 6800 GT is behind the poor performances of the Radeon X1650 Pro.



The HDR mode is based on FP16 and the GeForce FX 5900 XT, Radeon 9800 Pro, and X800 XT PE don’t support it.

Rainbow Six Vegas

Rainbow Six: Vegas

We measured performances in the introduction scene and 4x anisotropic filtering was activated via drivers.



Without HDR, banding is strongly noticeable in shadows. To unburden the graphic card in HDR, all options were set to a minimum. The game requires Shader 3.0 support, and, therefore, the oldest cards don’t work. Amongst the others, ATI clearly dominates.



In high quality mode, HDR enables the banding to disappear. Note that we activated low quality for shadows (light filtering, character shadow) instead of a very low quality (no filitering and no character shadow), because with higher settings there was too much of a performance drop.

Need for Speed Carbon

Need for Speed Carbon

We carry out a precise reproducible trajectory, which is always the same.

Anisotropic filtering was activated.



Once again the Radeon dominate. GeForce performances have problems in this recent game, however, Nvidia didn’t react on the driver level. If you have a GeForce card you will just have to make do with the inferior quality. A Radeon 9800 Pro even beats the GeForce 7600 GT !

The same results.


What we call HDR mode in Need for Speed Carbon consists of the activation of high quality post processing filters and motion blur, which need 3.0 shaders and HDR. The GeForce FX and Radeon 9800/X800 therefore can’t use it. For the others, ATI comes out largely on top.

Performances in HD video reading

Video performances

Decoding high definition video requires a very high calculation power. This can pose a problem if the CPU isn’t up for the task and is more of a risk for AGP systems. GPUs offer hardware assistance for this decoding, which is more or less efficient depending on the model. This test was carried out with an Athlon 64 3700+ and Power DVD 7.3 Ultra final.

First off, we measured CPU use with a trailer in H.264 720p:


You may have noticed that results weren’t always logical, because the Radeon 9800 Pro, GeForce FX 5900 XT and GeForce 6800 GT were not supposed to accelerate this reading. However, they showed variable performances, which were better at times than cards with this capability! The GeForce 7600 GT was the card that came out the best in this test, however, overall the CPU was enough and the gap wasn’t that big.

Our second test was done with a trailer still in H.264 but this time in 1080p and with Power DVD Ultra 7.3 :

In these conditions, the differences between the cards that accelerated this reading and the others increased. The GeForce 7 do have an advantage over the Radeon X1000, but these figures aren’t definitive. We noticed with GeForce 7s set at lower frequencies, that fluidity wasn’t perfect and only Nvidia’s GeForce 7600 GT was satisfactory in this area (reading with the 6600 GT wasn’t possible). This is something we noticed already on several occasions with Purevideo and when GPU frequencies aren’t high enough. Deactivating hardware acceleration increases CPU use and fluidity is a little better than with acceleration, but not perfect as the CPU is limited. There was no problem with the Radeon X1000, which did not suffer from this problem, and although it takes less of a burden off of the CPU.

Our third test uses the HD-DVD presentation video in VC-1 format ("WMV") in 1080i and at a rate that varies between 15 and 30 mbps :


None of the solutions could read the video correctly and this with all the latest official drivers. The Radeon X1000 were the only ones able to do this, however, without any real acceleration. As the CPU was insufficient, video wasn’t fluid. Starting this test on the GeForce 6 and 7 led to failure of PowerDVD as soon as it was open. The Radeon 9800 Pro, Radeon X800 XT PE and GeForce FX 5900 XT refused to read this PowerDVD video, indicating that their drivers aren’t reliable. In theory, this is a security measure imposed by Cyberlink in order to prevent the pirating of its software, and with which market players have blocked the reading of their media.

These results aren’t that great for AMD and Nvidia, who use the processing capability of HD video as one of their prime marketing points. This is indicative of another problem. The quality of support in this area is inexistent, and this means we can’t have full faith in its capabilities. Software as much as drivers are as much to blame, however, this of little importance, because promises to users weren’t fulfilled. Maybe it’s time that the very architecture of the access to help systems of video reading be reviewed. If AMD and Nvidia aren’t capable of providing a universal video interface that is efficient and robust in their drivers, perhaps this idea should be abandoned. And why not simply create a library where developers can have access to this software? This could avoid many problems…

Conclusion

Conclusion

This review, which is probably the last devoted to AGP graphic solutions, leads us to several conclusions. It also confirms some other impressions.

HD content is slowly starting to make its widespread presence felt and will need significant processing power to be decoded. This is a critical blow to an ageing AGP configuration. Graphic cards can be of help on this level, however, they do not fulfil the role claimed by manufacturers.

AMD as much as Nvidia refuse to be clear on the real capacities of their video technology. What card can read HD-DVD or Blu-ray ? Which CPU should go along with it? If a card is limited, what is the exact limit?

Instead of giving concise answers, AMD like Nvidia are simply riding the HD wave and do not provide reliable solutions to users. To this we can add the recurrent problems of drivers that function more or less according to their version and software used. In other words, if you have an AGP system and would like to play HD-DVD or Bluray, we don’t recommend a graphic upgrade at this time. Instead, consider adding a powerful dualcore CPU if your system is compatible or altogether changing platforms.


In terms of 3D, performances depend partly upon drivers, for which optimisation efforts diminish with time for any given GPU. This leaves us to consider the delicate question of when a manufacturer should shift optimization efforts from one generation of GPUs to another. Let’s remember that the more significant an architectural change is, the less it is possible for optimizations that will benefit more than one line of GPU. We also have the impression that ATI cards have aged better than Nvidia ones, or perhaps paradoxically, Nvidia has integrated new revolutionary technology a little earlier. If today a 6800 has poor performances and doesn’t really allow us to use Shader 3.0 and HDR to their fullest, it did allow games to evolve. A X800 did give the user more direct utility, while the GeForce 6800 is of benefit to GeForce 7 or 8 and Radeon X1000/2000 owners.

The driver component seems to be to the advantage of AMD’s current GPUs in the long term. However, we should take into account that this isn’t entirely dependant on AMD and Nvidia efforts in this domain as these cards aren’t the most important on the market. Delays in ATI/AMD material have allowed development teams to concentrate more on products on the current market. Whatever the case, it seems obvious that optimization efforts for the GeForce 7 and specifically with Windows XP is in decline and this is of consequence for those who want to update their AGP systems. In other words, regardless of the reason, software support is relatively better for AMD with current AGP solutions and we recommend you take this into account.

As for the graphic cards themselves, in more recent games, ATI solutions dominate. This is partly because Nvidia has abandoned AGP and for the above mentioned reasons. The Radeon X1950 and X1650, thus have better performances in games. If you do not want to change platforms, have a CPU that is apt for games, and want to change graphic cards, we recommend either a Radeon X1650 XT or Radeon X1950 Pro, depending on your budget. These cards have a good performance price ratio and are relatively silent, notably with PowerColor, which opted for an Artic Cooling system on its X1950 Pro AGP.

Note that Gecube offers a Radeon X1950 XT AGP, but it’s rather hard to find. A GeForce 7950 GT AGP should be available at the end of the month from several manufacturers (already available from XFX in some countries), and we will update this article if we can get are hands on one.

Finally, we finish with a word on GeForce FX 5900 XT performances, which clearly shows what can happen when a manufacturer makes a mistake on architecture. If Nvidia was capable to create an illusion for some time with strongly optimized drivers, reality eventually caught up with them as DirectX 9 games became more common. These cards don’t function with current games.