X-bit labs

NVIDIA NV18/NV28 and AGP 8x Investigation /part 2/

Category: Video

by FastSite

[ 12/06/2002 | 12:00 AM ]

On September 25, NVIDIA introduced its new graphics chips supporting the AGP 3.0 standard and 8xdata-transfer speed. The chips boasted higher working frequencies as well. But what hides behindthese praised innovations? What are the advantages? Read the review to find out the truth!

3D Performance: SiS648 Based System

NVIDIA GeForce4 MX440 with AGP 8x

We will start in ordinary modes, without anti-aliasing and anisotropic filtering:

Unreal Tournament 2003 pays no attention to the change of the AGP mode and data-transfer rate. There is no difference at all in performance of NVIDIA GeForce4 MX440 with AGP 8x in different AGP modes.

But the NVIDIA GeForce4 MX440 based card overclocked to the frequencies of the new 8x one cannot catch up with it, though. The reasons can be numerous: different memory timings, BIOS's, different GPUs…

When running at its nominal frequencies, GeForce4 MX440 loses notably to GeForce4 MX440 with AGP 8x. It's really not surprising, as the latter has higher nominal frequencies.

It's all the same: NVIDIA GeForce4 MX440 with AGP 8x can boast no advantage in AGP 8x mode. The tiny difference in results can be written off as a measurement error.

GeForce4 MX440, overclocked to the level of the competitor, still falls behind it a little bit.

At nominal frequencies, GeForce4 MX440 appears considerably slower than GeForce4 MX440 with AGP 8x because of the difference in their frequencies: the graphics card based on GeForce4 MX440 with AGP 8x has 1.8% higher GPU and 28% higher graphics memory clock-rates.

No changes here: AGP 8x provides no evident results improvement.

It looks as if testing in "normal" modes hardly loads the AGP bus. All the textures stacked up nicely into the local graphics memory and the graphics cards didn't have to resort to texture uploading and AGP-texturing. The transfer of polygons didn't load the AGP much, too. One way or another, the graphics card based on NVIDIA GeForce4 MX440-8x got no real advantage through its higher AGP bandwidth.

Now we will increase the workload by turning on full-screen anti-aliasing and anisotropic filtering. The local memory amount reserved for textures will be smaller and the higher AGP bandwidth may come in handy:

Well, AGP 8x improved the performance in Quake3 Arena and Serious Sam: The Second Encounter, but the actual growth is just laughable.

So, the results indicate that during the tests of our NVIDIA GeForce4 MX440 with AGP 8x graphics card in a SiS648based system we couldn't see any benefit from the new AGP 8x.

However, the increased clock-rates of the card allowed it to beat its predecessor and turned to be the real advantage.

NVIDIA GeForce4 Ti4200 with AGP 8x

The graphics cards based on NVIDIA GeForce4 Ti4200 and GeForce4 Ti4200 with AGP 8x have twice as much graphics memory compared to GeForce4 MX440/MX440 with AGP 8x based cards, so there is even smaller chance that the game would require texture uploading or AGP-texturing.

The benchmarks proved our concerns: AGP 8x mode adds no benefits to the GeForce4 Ti4200 with AGP 8x.

Nevertheless, its increased graphics memory clock-rate provided 10% performance growth over the GeForce4 Ti4200 based card.

Now we are turning on anti-aliasing and anisotropic filtering:

And here again we can't see any effect of the praised AGP 8x.

So, the tests of the new graphics cards on SiS648 make it clear that for now they have only one advantage over their predecessors: higher working frequencies. Enabling AGP 8x mode led to no performance growth, at least in case of a SiS648 based platform.

3D Performance: VIA KT400 Based System

NVIDIA GeForce4 MX440 with AGP 8x

Unreal Tournament is still indifferent to all our manipulations with the AGP modes.

There is definitely something wrong with Quake3 Arena. Why does AGP 3.0 provide poorer results than AGP 2.0?

Note also that the higher is the resolution, the smaller is the gap between the AGP 3.0 card and its rivals. As we already know, the cards don't use AGP-texturing here, so the problem with speed may only be connected with the polygons transfer. The number of polygons in the scene is the same in all resolutions, as well as the time required to transfer the polygons via the AGP bus. That's why when the resolution is higher and it takes longer to build all frames, these constant delays become less prominent and affect the overall result not that greatly.

The story goes on: whatever the data transfer speed is, the graphics card does worse in AGP 3.0 mode, than in AGP 2.0 mode. The lower is the resolution, the bigger is the gap in results.

Well, there is a certain solace, though. The GeForce4 MX440 with AGP 8x has higher working frequencies, so it always outperforms the regularly clocked GeForce4 MX440.

If we compare NVIDIA GeForce4 MX440 with AGP 8x with GeForce4 MX440 in AGP 2.0 mode and with equally set frequencies, the new one will turn a little faster.

With the enabled full-screen anti-aliasing and anisotropic filtering the new graphics card still does worse in AGP 3.0 mode than in AGP 2.0. But here the gap is smaller than in the previous tests, due to higher workload on the graphics cards. Certain differences in BIOS, memory timings and GPU design allow the new card to perform better even in AGP 3.0 mode compared with its predecessor "overclocked" to the level of GeForce4 MX440 with AGP 8x.

NVIDIA GeForce4 Ti4200 with AGP 8x

NVIDIA GeForce4 Ti4200 with AGP 8x on the VIA KT400 based testbed behaves the same as GeForce4 MX440 with AGP 8x.

Full-screen anti-aliasing and anisotropic filtering increase graphics card workload, so the performance gap in AGP 3.0 mode gets smaller than in case the tests are run without the enabled FSAA and anisotropic filtering.

Conclusion

So, the test results suggest that you'll hardly get any performance boost in present-day games with AGP 3.0 8x and double AGP bandwidth. Even if the performance gets any better, this will be a really insignificant improvement.

When rolling out renewed GeForce4 Ti and GeForce4 MX with AGP 8x support, NVIDIA made a very wise move having considerably increased their clock-rates. The new graphics cards turned out to owe their performance growth to the higher working frequencies, and not to the AGP 8x support.

Anyway, the company once again managed to present its developments as something brand-new and earn a lot on its "old-new" GPUs with the minimal effort applied.

And what a nice opportunity for graphics cards makers! A colorful package, magic "AGP 8x" letters and a name like "GeForce4 MX480", as we see by the Albatron card: all this helps to entice the customer. And there will be customers for these "brand-new" and "up-to-date" graphics cards…

The same makes sense for chipset and mainboard makers. AGP 8x is a nice opportunity to roll out "ultra-modern" products. And if we can't say anything bad about SiS648 based mainboard, since the graphics card worked in AGP 3.0 mode at least not worse than in AGP 2.0, the functioning of the VIA KT400 based board couldn't keep us silent.

When AGP 3.0 mode was enabled, at any data-transfer rate, all the changes in AGP 3.0 specs are forced into action. And it's not important whether the OS "knows" about AGP 3.0, or not. In other words, the problems with AGP 3.0 in KT400 may lie on the hardware level, i.e. in the chipset itself, as well as in BIOS, drivers or traditional "4-in-1" from VIA.

But really, I don't care about what and where they did wrong with the chipset. Imagine that I got so much impressed with AGP 3.0 features that I made up my mind to buy a VIA KT400 based mainboard, an AGP 8x graphics card and where am I? AGP 8x does work, but the speed would be lower than in AGP 2.0 4x. Hm, doesn't seem to be what I have longed for?

There is still some hope left that the problems of KT400 have nothing to do with hardware, but lie in software, and can be cured in the new BIOS, "4-in-1" versions and so on. Otherwise, we may witness another proof of VIA's chipsets development law: rapid introduction of some "KT400A".

But what about the AGP 8x standard? The higher bandwidth will only be useful when there are really big amounts of data pumped through AGP and AGP bandwidth is a crucial parameter for games. It may come, as there appear DirectX9 games that will be able to load the newest ATI and NVIDIA products with data amounts proportional to their powerfulness.

The AGP 8x story doesn't end here. There are two more AGP 3.0 supporting chipsets: NVIDIA nForce2 and Granite Bay from Intel. Moreover, we have only tested graphics cards based on NVIDIA's chips, while there are new AGP 8x cards based on ATI RADEON 9700 PRO/ RADEON 9700/ RADEON 9500 PRO/ RADEON 9500 and on SiS Xabre 600/400. Stay with us for more! :)