GeForce 7800 GTX Performance with Athlon 64 July 21, 2005 Brandon Sandman Bell

Introduction

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What! It’s too fast? How does this happen?

On the software side, even the latest games often lag behind the newest hardware by 6-12 months. This is because hardware cycles are refreshed so quickly today that game developers can’t keep up. Whereas ATI and NVIDIA often replace their latest products every six months, a game can take (at best) 1-2 years to develop, if not longer. By the time a game is developed from start to finish, the 3D graphics landscape may have advanced by a generation or two.

In other cases publishers rehash the same outdated game engine over and over again. This often happens with sports titles which are typically refreshed every year. In some instances games can even be CPU-limited due to poor programming.

But software isn’t the only aspect that can hold back a next-gen card at launch, another culprit is often the CPU.

Quite simply, with next-gen graphics processors delivering 1.5-2X times more performance than their predecessors at launch, the CPU can become a bottleneck in many titles we test with. After all, the clock speed of new CPUs tends to only increase in increments of 100-200MHz; only delivering about 10% more performance with each new processor release.

How can you tell when you’re CPU-limited? You can see this in benchmarks where you hit the same frame rate regardless of graphics settings (such as increasing screen resolution). As soon as a faster CPU is inserted, your frame rates increase.

This is a situation you’d like to avoid if you’ve just plunked down $600 on a brand new 7800 GTX graphics card, as you’re not getting the most from your money (although being CPU-limited does allow you to crank up the image quality settings for “free”, as you won’t get the performance hit usually associated with these setting changes).

In this article, we’ll attempt to break down what clock speed(s) you should shoot for if you plan on upgrading to a GeForce 7800 GTX. Our platform for today is the nForce4-based Athlon 64, as this platform is the solution of choice for most gamers right now.

The processors…a quick refresher

Sorting through AMD’s current Athlon 64 lineup can be a sizeable task. Not only do you have to worry about Athlon 64 versus Athlon 64 FX (and don’t forget the X2), but you also can’t forget AMD’s newer 90-nanometer processors. Besides the newer manufacturing process, these chips bring with them support for 11 of Intel’s 13 SSE3 instructions, lower operating voltage, and contain a tweaked memory controller which supports mismatched DIMM sizes as well as providing support for all DIMM slots to be populated without a performance slowdown. Athlon 64 cores based on this new 90-nm revision go by the name of “Venice” and contain 512KB of L2 cache, just like previous A64 processors.

On the FX side, the 90-nm chip you should be on the lookout for is San Diego. San Diego sports all the same enhancements first introduced with Venice, only as an FX processor, San Diego chips ship with a 1MB L2 cache.

For our testing, we used a Venice-based Athlon 64 3000+ and 3500+, while our 3800+ is based on the older Newcastle core (unfortunately, we weren’t able to snag a Venice-based 3800+). Our 4000+ and FX-55 are based on AMD’s ClawHammer core, while the FX-57 is built on AMD’s San Diego core. Keep in mind that the 4000+ is essentially the FX-53 in disguise, as it sports the same clock speed and cache size, only it ships with a locked clock multiplier.

Finally, we’ve also thrown in a GeForce 6800 GT, so you can see how this popular card scales in comparison to the 7800 GTX. It’s quite possible that there may be some cases where a 6800 GT equipped with a speedy processor may outperform the 7800 GTX with a slower chip, so it’s important to check for that situation.

Test Systems

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System Setup

AMD Athlon 64 FX-57
AMD Athlon 64 FX-55
AMD Athlon 64 4000+
AMD Athlon 64 3800+
AMD Athlon 64 3500+
AMD Athlon 64 3000+

ASUS A8N-SLI Deluxe

1GB OCZ DDR400 SDRAM

NVIDIA GeForce 7800 GTX
NVIDIA GeForce 6800 GT
Driver version 77.72

250GB Maxtor Hard Drive Maxline III SATA Hard Drive w/16MB Cache

Windows XP Professional SP1

DirectX 9.0c

Benchmarks

Pacific Fighters
IL-2 Sturmovik: Forgotten Battles
Lock On: Modern Air Combat
Far Cry 1.31
DOOM 3
Half-Life 2
Battlefield 2

Notes

Technically, purists may insist that CPU-scaling results should be taken at the lowest resolution possible (640x480 or 800x600) with image quality settings turned down, and no AA/AF. For the most part, we decided not to do this for our tests, as it isn’t something a prospective 7800 GTX or 6800 GT owner would do with their card. However, we did run a few tests with F.E.A.R. without AA/AF, although we kept the graphics settings cranked up.

Frequency Scaling – Shooters

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Notes

Before we examine the GeForce 7800 GTX’s performance with specific processors from AMD’s lineup, let’s first take a look at how well the 7800 GTX card scales at various clock speeds. This will give us a basic idea of what clock frequencies the 7800 GTX begins to respond to.

In order to test this, we took our FX-57 chip and use its unlocked multiplier to play with a range of clock speeds. In this case, we’ve decided to start at 1.8GHz, and work our way up to 2.8GHz.




Performance in the beta build of F.E.A.R. improves by 2% when going from 1.8GHz to 2.0GHz, and 7% in Half-Life 2. The margins improve once we hit 2.2GHz, with the 2.2GHz/7800 GTX combination outrunning the 2.0GHz system by 8% in Half-Life 2 and 3% in F.E.A.R. beta. From there, the performance improvements continue as we hit higher clock speeds in both applications, although the margins aren’t quite as high, with each 200MHz improvement buying us roughly another 4-5% in Half-Life 2 performance, and at most, 3% in F.E.A.R. beta.

Frequency Scaling – Flight sims

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Once again the GeForce 7800 GTX really begins to shine once we hit 2.2GHz, performance improves by 9% in both applications. Like Half-Life 2 previously, IL-2 Sturmovik scales a little better than LOMAC as we increase clock speeds – in fact going from 1.8GHz to 2.0GHz buys us another 9% in performance, and we continue to see a nice improvement when going from 2.2GHz up to 2.4GHz.

Pacific Fighters

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Pacific Fighters - OpenGL

Far Cry Training

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Far Cry – Direct3D

IL2	Page:: ( 7 / 15 )

IL-2: FB – OpenGL

LOMAC

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LOMAC – Direct3D

DOOM 3 High Quality

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DOOM 3 – OpenGL

Half-Life 2

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Half-Life 2 – Direct3D

Splinter Cell

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Splinter Cell – Direct3D

F.E.A.R. Beta

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F.E.A.R. 4xAA/8xAF

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Battlefield 2

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Battlefield 2 – Direct3D

Conclusion

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NVIDIA’s GeForce 7800 GTX is an incredibly powerful graphics card. Sporting an increased number of pixel and vertex pipelines, higher clocks, and the enhancements NVIDIA has made to its G70 core, the 7800 GTX is a more than capable performer, delivering performance 1.5-2X times greater than its predecessor, the GeForce 6800 Ultra in some cases.

If you’re not careful however and pair the 7800 GTX with a slower processor, all that power can go to waste. This is because the processor isn’t fast enough to keep up with the graphics card. An analogy we’ve used in the past is putting 14” tires on a Ferrari.

Just as a 14” tire wouldn’t be capable of providing the traction needed for the Ferrari to accelerate, a slower processor prevents the 7800 GTX from hitting higher frame rates. Fortunately, AMD’s Athlon 64 processors are fast enough to keep the 7800 GTX sufficiently fed, although we obviously saw that the Athlon 64 3000+ was preventing the 7800 GTX from reaching its full potential in many cases.


Based on our testing, the sweet spot kicks in somewhere around the A64 3500+ range. Our numbers with Half-Life 2 show this most dramatically. In addition, the HL2 1024x768 results also show that the 7800 GTX benefits from the 1MB L2 cache of the 4000+ and FX processors. The scaling results on page three corroborate these findings as well, as the 7800 GTX’s performance jumps profoundly at 2.2GHz. This is probably the clock speed you should shoot for if you’re in the market for a new processor but don’t want to drain your bank account in the process; or if you can’t afford a new chip, it’s definitely the speed you should go for when overclocking.

If you’re lucky enough to afford a GeForce 7800 GTX SLI setup, you should definitely set your goals higher. In our GeForce 7800 GTX Performance Preview article, we were CPU-bound in many cases with the 7800 GTX SLI configuration even when running with an FX-55 CPU, which was the fastest processor we had at the time. We wouldn’t be surprised if 3.0GHz or more was required to truly keep a 7800 GTX SLI config running optimally.