GeForce 6800 Performance and Overclocking June 14, 2004 Brandon Sandman Bell

Introduction

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GeForce 6800: The wait is almost over

It has nearly been two months since NVIDIA first announced its next generation graphics core, GeForce 6800/GeForce 6800 Ultra, and a little over a month since NVIDIA’s 6800 GT plans were unveiled, with only a trickle of cards hitting retail – weeks behind ATI’s RADEON X800 PRO and behind NVIDIA’s own schedule for the 6800 parts. But fortunately for you NVIDIA enthusiasts out there we can report that the wait is nearly over, in fact we saw quite a few innovative GeForce 6800 cards at Computex in Taiwan last week.

In fact, the first retail GeForce 6800 board has arrived for review, Leadtek’s WinFast A400 TDH. Having a final, retail board in hand is definite confirmation that a tidal wave of NV40 boards is about to be unleashed on the market. Leadtek and Gainward are also in the final stages of shipping their GeForce 6800 Ultra cards to retail as well.

Personally, we think it’s exciting to see the more mainstream enthusiast-level cards released to the market first. If you recall previous next generation releases, the ultra high-end boards are typically released initially: RADEON 9700 PRO shipped months ahead of RADEON 9700, while NVIDIA’s GeForce FX 5900 Ultra just beat the 5900 to market and was released well in advance of GeForce FX 5900 XT, and on the DX8 side, GeForce4 Ti 4600 and GeForce 3 predated less expensive variants by multiple months.

Based on our talks with ATI and NVIDIA’s board partners, both companies are having a difficult time with their high-end parts, we reported on this in our Computex report last week. Apparently, yields on graphics cores aren’t the issue, at least for ATI, the bottleneck lies elsewhere. We have a strong suspicion that GDDR3 memory is the culprit.

In any case, for whatever the reason, it’s good to see the cheaper graphics cards hitting retail as few gamers can afford the stratospheric prices ATI and NVIDIA are asking for the GeForce 6800 Ultra and RADEON X800 XT Platinum Edition. Often times, with a little bit of overclocking, the cheaper boards can be tuned to perform similarly to each respective company’s high-end offering. This is what we’ve set out to do for this article -- explore the performance and overclocking potential of NVIDIA’s GeForce 6800.

Since the GeForce 6800 was first announced, we were eager to see how it stacked up to NVIDIA’s other 6800 offerings, and we bet you were too. But since we have another trip up north coming this weekend, we wanted to get the piece up before departing. We’ll have the full Leadtek review up when we return next week with additional cards and performance analysis included.

Core details

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The NV40 core powering NVIDIA’s GeForce 6800 enjoys an impressive feature set. Rather than adapt previous GeForce FX architectures, NVIDIA has employed an entirely new design for the 6800 family.

It all starts with the graphics core’s 16 pixel pipelines, twice that of previous graphics architectures. When combined with the GeForce 6800’s six vertex engines, the graphics core’s pixel processing power is significantly increased as is fill-rate. Basically, this allows the GeForce 6800 to pump a lot of triangles.

NVIDIA clocks the GeForce 6800 graphics core at 325MHz, which may sound like a low figure at first, but when you factor in the core’s 12 pipelines, the GeForce 6800 packs a respectable fill rate of 3.9 Gigatexels/second and a peak pixel fill rate double that of GeForce FX 5950 Ultra.

Paired alongside the GeForce 6800 core is 128MB of DD1 memory clocked at 350MHz (700MHz effective). Like previous GeForce FX 5900 series graphics cards, the 6800 features a 256-bit wide memory interface, which is responsible for keeping the NV40 graphics core fed with up to 22.4GB/sec worth of data. It’s this figure that could be the 6800’s greatest weakness; the memory subsystem of ATI’s RADEON 9800 XT provided its core with 23.4GB/sec of peak memory bandwidth, while the 5950 Ultra tops out at an impressive 30.4GB/sec. This could potentially put the GeForce 6800 at a disadvantage in situations where you’re memory bandwidth-bound. Such cases would occur at high screen resolutions and/or anti-aliasing and anisotropic filtering cranked up.

Board manufacturers can also outfit their GeForce 6800 board with 256MB of DDR1 memory.

If you need a little more performance, NVIDIA also offers the GeForce 6800 GT and GeForce 6800 Ultra. Both cards feature 16 pixel pipelines instead of the 6800’s 12, while the core and memory clock frequencies have been bumped up significantly as well: 400MHz core/550MHz memory on the GeForce 6800 Ultra, and 350MHz core/500MHz memory on the 6800 GT, both ship with 256MB of GDDR3 memory.

Shader Model 3.0

Of course, another key highlight NVIDIA has incorporated into GeForce 6800 is support for shader model 3.0. Shader model 3.0 builds on the specs of shader model 2.0, supporting more instructions and dynamic flow control (looping/branching). FP32 is also the minimum precision in shader model 3.0, versus FP24 in previous shader models.

Finally, support for features such as high dynamic range lighting are provided as is vertex processing with textures and centroid sampling. We provided a more detailed look at the new additions in shader model 3.0 as well as NVIDIA’s new graphics core in our GeForce 6800 Ultra Performance Preview. Please refer back to it for more details.

Image quality

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Since we’re testing the GeForce 6800 card with a new driver, we felt it was important to go over the card’s image quality. We won’t go into quite as much depth as before as we’re pressed for time, but we did want to demonstrate the visuals NVIDIA’s GeForce 6800 is capable of dishing out.

Anti-aliasing

In our GeForce 6800 Performance Preview, we gave the AA crown to ATI, however in our X800 article, we re-examined a few scenes and found areas where NVIDIA excelled. Quite simply, with NVIDIA’s new rotated-grid sample pattern, their AA quality has improved substantially. While there are still differences between the two architectures, the distinctions between the two cards aren’t as apparent. Check out these screenshots taken in LOMAC:

[image]

GeForce 6800


RADEON X800 PRO

GeForce 6800


RADEON X800 PRO

Anisotropic filtering

There has been lots of controversy surrounding ATI’s filtering algorithms lately. In order to provide the fairest comparison, we decided to leave optimizations on for both companies, but we’ll implore ATI to do the same we asked NVIDIA around this time last year: provide a setting to disable them. NVIDIA provides a full trilinear option in its latest driver (although it’s disabled by default), hopefully ATI will follow suit shortly.

[image]

GeForce 6800


RADEON X800 PRO

Test conditions

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System Setup

AMD Athlon 64 3800+

ASUS A8V Deluxe

1GB Corsair XMS3200 DDR SDRAM

ATI RADEON X800 PRO
Driver version CATALYST 4.6

NVIDIA GeForce 6800 Ultra
NVIDIA GeForce 6800 GT
NVIDIA GeForce 6800
eVGA e-GeForce FX 5950 Ultra
Driver version ForceWare 61.34

30GB IBM Deskstar DTLA 307030 ATA/100 Hard Drive

Windows XP Professional SP1

DirectX 9.0b

Benchmarks

Lock On: Modern Air Combat (Mig-29 custom demo)
Call of Duty (demo0032 custom demo)
Unreal Tournament 2004 (T3 custom demo)
IL-2 Sturmovik: Forgotten Battles (The Black Death track)
Splinter Cell (FS custom demo)
Tomb Raider: Angel of Darkness (Beyond3D custom demo)
Far Cry (custom demo)

Call of Duty

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Call of Duty – OpenGL

IL-2 Sturmovik: Forgotten Battles 4xAA

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IL-2 Sturmovik: FB - OpenGL

IL-2 4xAA/8xAF

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IL-2 Sturmovik: FB - OpenGL

Lock On: Modern Air Combat

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Lock On: Modern Air Combat – Direct3D

LOMAC 4xAA

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Lock On: Modern Air Combat – Direct3D

Splinter Cell

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Splinter Cell – Direct3D

Tomb Raider

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Tomb Raider – Direct3D

Tomb Raider 4xAA

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Tomb Raider – Direct3D

UT 2004

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Unreal Tournament 2004

UT 2004 4xAA

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Unreal Tournament 2004

Far Cry

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Far Cry – Direct3D

Far Cry 4xAA

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Far Cry – Direct3D

Far Cry 4xAA/8xAF

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Far Cry – Direct3D

Overclocking

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Far Cry – Direct3D

Call of Duty

Conclusion

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Despite its slower clock speeds, the GeForce 6800 is still a good performer. This is made possible due to its NV40 graphics core, which sports 12 pixel pipelines and a 325MHz graphics core. As a result of this combination, the GeForce 6800 has just enough pixel processing power and fill rate to outperform its predecessor, GeForce FX 5950 Ultra in most situations. In some cases, the margin is hardly noticeable, a perfect example of this would be in Lock On: Modern Air Combat. In fact, with AA enabled the 5950 Ultra comes out on top at high resolutions. Performance in Call of Duty was close between the two cards as well.

In other titles, the GeForce 6800 owns a decisive advantage. This was the case in UT and Splinter Cell, as well as Far Cry for the most part.

Considering the GeForce 6800’s shader model 3.0 support and its $300 price tag, it should definitely be an option among those of you who were shopping in that price range. Graphics cards that currently reside in that space include the GeForce FX 5950 and RADEON 9800 XT, so we have a feeling that the 6800 will do well for NVIDIA here: based on what we’ve seen, the GeForce 6800 is basically a well-oiled GeForce FX 5950 Ultra with shader model 3.0. This ensures the longevity of the board through at least 2005.

The real question for enthusiasts though is GeForce 6800 GT and RADEON X800 PRO. NVIDIA has detuned the GeForce 6800 just enough that for $100 more, you can get a more powerful graphics card, ensuring excellent performance in a wider variety of applications or with higher image quality. Many gamers will likely gladly pay a premium for this. Because of this, it will be important to see final street prices for the GeForce 6800/6800 GT and RADEON X800 PRO.

NVIDIA has prepared itself for this by going with more traditional DDR1 memory clocked at 350MHz, whereas the 6800 GT and X800 PRO are both GDDR3-based boards. When you couple this with the aggressive pricing NVIDIA and its board partners have shown in the past, a $250 GeForce 6800 card would not be inconceivable a few months from now.

Of course, ATI is rumored to be ready for this contingency, should it occur. The pipelines within the X800 graphics core can be disabled without affecting the rest of the chip. Because of this, it’s believed ATI may answer the GeForce 6800 with an 8-pipeline X800 SE board of their own. For right now though, the GeForce 6800 is the king of the lower half of the high-end segment.