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Unlocking the GeForce 6800 May 24, 2005 Brandon Sandman Bell |
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Summary: Earlier this month we took a look at EVGA's e-GeForce 6800 graphics card. In the review, we gave the card high marks for its excellent price/performance ratio. But what if you could turn NVIDIA's 12-pixel pipeline, $200 GeForce 6800 into a 16-pixel pipeline/6 vertex unit card for free? In today's article, that's exactly what we did! See how the 16-pixel pipeline/ card performs as well as the 12-pipe GeForce 6800 with 6 vertex shaders. Is the card able to take down GeForce 6800 GT and RADEON X800 XL? Find out in this article!
 Introduction | Page:: ( 1 / 13 ) |
This has huge ramifications for enthusiasts looking to get the most bang for their buck because the GeForce 6800 boasts a number of features that make it more powerful than the GeForce 6600 GT.
For starters, the GeForce 6800 sports a 12-pixel pipeline architecture, with five vertex engines pumping up to 406 million triangles/second (3.9 Gigatexels/sec fill rate). The GeForce 6600 GT features fewer pixel and vertex pipes, but attempts to make up for this by running at much higher clocks, 500MHz on the 6600 GT versus 325MHz on the GeForce 6800.
The real advantage the GeForce 6800 enjoys over the GeForce 6600 GT however is in its memory subsystem.
The GeForce 6800 features a 256-bit memory interface, with four 64-bit memory controllers paired to either 128MB or 256MB of DDR memory running at 350MHz (700MHz effective). This gives the GeForce 6800 up to 22.4GB/sec of peak memory bandwidth, 6.4GB/sec more than GeForce 6600 GT. As a result, the GeForce 6800 really shines against the GeForce 6600 GT at high screen resolutions with anti-aliasing turned on. You saw this a few weeks ago in our EVGA review with 4xAA/8xAF. In multiple cases at resolutions of 1024x768 (and up) the GeForce 6800 card was running 20% faster or more.
But what if you could turn the 12-pipeline GeForce 6800 into an even more powerful 16-pipeline card without spending a dime? That’s exactly what many of you asked us to do a few weeks ago with EVGA’s e-GeForce 6800, so guess what? We did!
In order to understand how this is possible, it’s best to go over the GeForce 6800’s architecture first.
Optimizing NV40’s manufacturing process
As you probably know by now, the GeForce 6800 is based on NVIDIA’s NV40 graphics core. In AGP form, this is the exact same chip NVIDIA uses for GeForce 6800 Ultra and GeForce 6800 GT, only it has four of its pixel pipelines disabled, and one vertex unit turned off. (More specifically, NV40 sports sixteen pixel pipelines, these pipelines are organized into groups of four and are known as “quads”. The GeForce 6800 GT and Ultra have all four quads running with four pixel pipelines per quad for a total of 16 pixel pipelines. In GeForce 6800, NVIDIA turns off one of the four quads, leaving only three quads running for a total of 12 pipelines).
Why does NVIDIA do this you ask? In order to decrease manufacturing costs, NVIDIA (like all semiconductor manufacturers) uses tactics such as tweaking clock speeds and disabling features on their chips in order to service multiple markets with what is essentially the same product.
In the case of the NV40 family, the chips that are verified and tested to run at the highest clock speeds are put into GeForce 6800 Ultra cards, while those that just miss the cut go into GeForce 6800 GTs. NVIDIA then played it safe and created a third NV40-based product, GeForce 6800. Typically whenever a brand new product is introduced, some chips just don’t cut the mustard and aren’t able to run at the required clock speeds (especially when its built on an untested manufacturing process). In NVIDIA’s case for NV40, they were concerned that some chips may not be able to hit the clock speeds they’d envisioned with all sixteen pipelines running. Rather than throw these chips away as waste, they instead go into GeForce 6800 cards.
It’s important to keep in mind that the above only applies to NVIDIA’s AGP GeForce 6800 products. For PCI Express cards, NVIDIA uses two distinct graphics cores, one with 16 pipelines for GeForce 6800 Ultra/GT (NV45), and the second, which is built from the start with only 12 pipeline. This is NV41 and goes into PCI-E GeForce 6800 cards.
| Production (cont’d)/Modding | Page:: ( 2 / 13 ) |
It’s because of this that PCI-E GeForce 6800 cards can’t be modded into 16-pipeline cards. Basically, their NV41 graphics core only features 12 pipelines so there’s nothing turned off at the factory. Since AGP-based GeForce 6800 cards are still built on NVIDIA’s 16-pipeline NV40 core, they can still be modified to run with 16 pipelines. (In theory it’s possible that you could potentially get lucky and find a PCI-E GeForce 6800 card that is built on NV45, but the odds of finding one of these cards are incredibly long).
What we’re here today to find out is how fast a GeForce 6800 vanilla modified to run with 16 pipelines can run. Let’s get started.
Modding the card
First, we’ve got to turn on the pixel and vertex pipelines. Since NVIDIA hasn’t physically disabled these pipelines, GeForce 6800 cards can be modded to run with 16 pipes via BIOS modification in software. This is known as software modding or softmodding. Softmodding is preferred by many enthusiasts because it’s easier and safer than hardware-based mods (i.e. you don’t have to grab a soldering iron or any other tools to physically modify the hardware).
Softmodding has the added bonus that if the mod doesn’t work, you usually can revert the hardware you’ve modded back to its original state. In other words, you can easily undo the changes you’ve made, sometimes with just a few mouse clicks. This is important in case your hardware doesn’t work properly after it has been modified (here we should also mention that modding your GeForce 6800 to run with 16 pipes will void your card's warranty, so proceed with care).
Fortunately, there’s a software utility out there that does all the hard work for you: RivaTuner. You can grab the latest version of RivaTuner right here, from Guru3D.
With RivaTuner 15.5 in hand, we set out to unlock the pixel and vertex pipelines in our EVGA e-GeForce 6800 card. First, we’ll unlock the GeForce 6800’s pixel shaders. This is accomplished by turning on the quad that’s been disabled by default at the factory. Once you load up RivaTuner, you’ll be greeted by the Main menu tab:
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From here you’ll want to click on the customize icon in the “target adapter” field, immediately you’ll be greeted by six icons. You’ll want to click the first one “low-level system settings”.
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Under the low-level system settings tweaks menu lie two tabs, “AGP” and “NVStrap driver”. In order to manipulate the shaders, click on the NVStrap driver tab.
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| Unlocking instructions (cont’d) | Page:: ( 3 / 13 ) |
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Next, it’s time to start customizing things. Change the “active pixel/vertex units configuration field from “determined by VGA BIOS” to “custom” then click the “customize” button. Now you’ll see all four quads that your NV40 chip supports up top, followed by the vertex units in the middle.
Notice in our screenshots how the very first pixel quad on our EVGA card says “disabled” for the first pixel unit? You’ll also see that the first unit is masked in the “HW masked field”. In order to turn it on, click the first pixel unit. You’ll immediately see a checkmark, indicating that the pixel unit is now turned on!
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Now it’s time to turn on the vertex unit that has been disabled. In the case of our EVGA card, this is vertex unit 3. Once again, click on it so you see the checkmark, which turns on the vertex unit.
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Once both are checkmarked, click “ok”. You’ll now be back at the NVStrap driver tab. From here you should see that all 16 pipelines have been enabled, as well as 6 vertex units. This is indicated in the “active pixel/vertex units configuration” field. In our screenshot, this field says “custom (16x1, 6vp)”. If you see this, it means you’ve successfully reconfigured your card to now support 16 pixel pipes, and six vertex pipes. If it says “(12x1, 5vp)” you haven’t turned them on yet.
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Now that you’ve got all the pipes up and running, you can check your work by entering RivaTuner again and checking to make sure that the “State” field in the NVStrap tab now says “enabled” for both the pixel and vertex units. If it still says disabled, that means you didn’t turn the pipelines on properly. Go back and try again.
Once you’ve got everything turned on, you’ll now want to boot up a few games or any other graphics-intensive programs that you have such as 3DMark to check for artifacts. If you see lots of artifacts or any other form of corruption on the screen, that means your card won’t run properly with all pixel and vertex pipelines enabled and you’ll have to disable them with RivaTuner. Just go back to the NVStrap are an uncheck them. A lot of users have reported that leaving the sixth vertex unit turned on and disabling the pixel units works successfully. This results in a 12 pixel pipe configuration, with six vertex units, rather than the stock GeForce 6800’s 12 pixel pipe/5 vertex pipe configuration.
In our game testing, we did note an increased level of artifacts once the card was modded, but the artifacts would only pop up occasionally and would usually go away after a few frames, then come back a minute or so later for a frame or two. It was nothing substantial basically, and some titles would cause artifacts more frequently than others (in Half-Life 2 for example, we very rarely saw artifacts).
Before we get to the benchmark results, we should note that the pixel/vertex shader units that are disabled from the factory will vary from card to card. For instance, a Chaintech GeForce 6800 card we tested had pixel and vertex units 3 disabled). Also, don’t check “Unlock professional capabilities, as that will attempt to convert your GeForce card into a Quadro. Remember that RivaTuner is a powerful app that can damage your card if you're not careful. Using it to mod your card will void your warranty.
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| Test Systems | Page:: ( 4 / 13 ) |
System Setup
Intel Pentium 4 3.4GHz “Prescott”
ABIT IC7-G MAX II Advance
1GB OCZ DDR400 SDRAM
ATI RADEON 9800 PRO
ATI RADEON X800 XT AGP
ATI RADEON X800 PRO AGP
PowerColor RADEON X800 XL AGP
Driver version CATALYST 5.4
NVIDIA GeForce 6800 Ultra
NVIDIA GeForce 6600 GT AGP
EVGA e-GeForce 6800
NVIDIA GeForce 6800 GT
Driver version 71.89
250GB Maxtor Hard Drive Maxline III SATA Hard Drive w/16MB Cache
Windows XP Professional SP1
DirectX 9.0c
Benchmarks
Pacific Fighters (kamikaze demo)
Far Cry 1.3
DOOM 3 (gameplay custom demo)
Half-Life 2 (turrent demo)
Chronicles of Riddick
3DMark 05
| 3DMark 05 Synthetic tests | Page:: ( 5 / 13 ) |
3DMark 05 – Direct3D
| 3DMark 05 game test results | Page:: ( 6 / 13 ) |
3DMark 05 – Direct3D
| Pacific Fighters | Page:: ( 7 / 13 ) |
Pacific Fighters - OpenGL
| Far Cry Volcano | Page:: ( 8 / 13 ) |
Far Cry – Direct3D
| Far Cry Training | Page:: ( 9 / 13 ) |
Far Cry – Direct3D
| Chronicles of Riddick | Page:: ( 10 / 13 ) |
Chronicles of Riddick – OpenGL
| DOOM 3 High Quality | Page:: ( 11 / 13 ) |
DOOM 3 – OpenGL
| Half-Life 2 | Page:: ( 12 / 13 ) |
Half-Life 2 – Direct3D
| Conclusion | Page:: ( 13 / 13 ) |
As you’d expect, turning on all of the NV40’s pixel/vertex pipelines brought an immediate performance improvement in all applications we tested. Of course, the performance increase varied depending on the application tested. In Chronicles of Riddick, we saw an improvement of anywhere from 5-8%, with the result varying depending on screen resolution. Far Cry saw even greater benefits, with the 16-pixel/6 vertex unit GeForce 6800 configuration outperforming the 12-pixel/5 vertex GeForce 6800 by 7-10% in the volcano level, with performance in the training map varying between 5-10%. DOOM 3 and Half-Life 2 also saw some pretty good performance gains. Pacific Fighters was really the only title that didn’t benefit from the extra pipelines. Sure, the numbers were a little higher, but well within the margin of error.
This game, like most flight sims, is just too CPU-bound to really let the 16-pipe GeForce 6800 card really flex its new muscles.
We also tested the most popular fallback configuration most users revert to if their card doesn’t run properly with all 16 pixel pipelines enabled; that is 12 pixel pipes with six (rather than five) vertex units. In this scenario, we barely noticed a performance difference, with the only application taking advantage of the extra vertex shader being 3DMark 05. Even there though, if you look at the game test results with the sixth vertex shader enabled, performance is practically indistinguishable over the 5 vertex unit GeForce 6800. We did see a tangible performance improvement in 3DMark 05’s complex vertex shader test though. In games, it was practically impossible to differentiate the performance between the GeForce 6800 with five vertex shaders versus the six shader card. Many gamers swear by this method though.
By now you’re probably wondering where our overclocking results are, after all we usually like to overclock everything we get our hands on. In this case however, all of our attempts to overclock three different GeForce 6800 vanilla cards were unsuccessful. We were able to easily unlock the pipes on all three cards, but with each of them we could never overclock the graphics core or memory, not even 5MHz. Whether we used RivaTuner to OC the boards or the NVIDIA control panel, each time we tested our settings the GeForce 6800 card would fail to pass the overclocking test. Even if we were able to hit the speeds we achieved in our EVGA e-GeForce 6800 review (400MHz core/810MHz memory), it still wouldn’t have been enough to catch up to say, a GeForce 6800 GT. The GeForce 6800, even with all 16 pixel pipes and 6 vertex pipes running, still gives up too much memory bandwidth to the GeForce 6800 GT to be a 6800 GT killer. The 6800 board’s 128MB frame buffer would also be a huge impediment to catching up to a GT.
Overall though it’s got to be pretty exciting to be able to unlock your GeForce 6800 card’s pixel and vertex pipes for a little bit more performance. Unlike overclocking, board temperatures are practically unaffected, so those of you looking for a little more performance from your GeForce 6800 may want to give this a try. Just be careful when working within RivaTuner, as some of the features within the program can damage your card if you're not careful. And of course, its use will void your factory warranty.