Here's the latest in our series of article based on the wiki. This is a how-to for overclocking your Nvidia 8800 GTS, a database of results from the internet and other useful information.

Introduction

In late 2006, NVIDIA announced the world’s first DirectX 10-capable mainstream GPUs to the market in the form of the top-end GeForce 8800GTX and the slightly lower performing (but still very powerful) GeForce 8800GTS, both based on the G80 graphics core. The GTS provided a video card that maintained much of the high performance of the GTX but at a significantly reduced cost. At the time of its release, the 8800 series firmly bested the performance of any of ATI’s high end parts, including the X1950XTX. When overclocked, the cheaper 8800GTS is capable of performing better than the more expensive 8800GTX, with many 8800GTS cards achieving GPU overclocks in the range of 20%. 

• G80 core
• 96 “stream processors”
• 5 ROPs, each of which can render 4 pixels, resulting in 20 “effective” ROPs
• 681 million transistors
• 500MHz core clock speed
• 1200MHz stream processor clock speed
• 800MHz memory clock (1.6GHz effective DDR speed)
• 320-bit memory interface
• 640MB or 320MB memory (depending on configuration)

Overclocking Methods

NVIDIA nTune

The NVIDIA-recommended method to overclock the 8800 GTS is to use NVIDIA’s own nTune application. This software provides many capabilities, including temperature and voltage monitoring, video card and system fan control, as well as options for overclocking both the video card as well as the motherboard and CPU. It should be noted that the coolbits registry tweak that is commonly used to overclock NVIDIA video cards will not work with the 8800 series at the time of this writing. nTune version 5.05 or later is required for 8800 series compatibility.

INSERT OVERCLOCKING INFO HERE INCLUDING FAN SPEED TESTS AND IMPACT ON OVERCLOCKING

Other Software

RivaTuner is one 3rd party overclocking tool that is very useful for overclocking the Geforce 8800 series due to its ability to independently manipulate the clock speeds of the GPU, VRAM, and Shader Processors. Using RivaTuner to overclock, either the maximum GPU or Shader clocks will often be higher than with other programs that link these two values together because one of these values acts as a bottleneck for the other. In the tested card, the shader processors were able to be overclocked by an amazing 200MHz higher when independently overclocked versus the linked overclock.

The main ATITool screen provides three separate pairs of GPU and memory clock speed adjustments, one each for 2D, 3D low power, and 3D high performance. The memory adjustments will be consistent across all three profiles, but any GPU speed adjustments can be made separately for each profile. Unfortunately, although ATITool allows for cooling fan speed adjustments on most video cards, as of version 0.27 Beta 2, this capability is not unlocked on 8800 series cards.

ATITool version 0.26 was used in this case, and version 0.27 Beta 2 was tested, and showed no significant differences.

There appears to be a slight incompatibility problem with the 8800GTS in ATITool. It can be quite difficult to set the desired clock speeds, as can be seen at right. At times, the clock speed sliders have no effect even on the clock speeds ATITool reports at the top right portion of the window. At other times, even though ATITool reports a GPU speed of 631MHz, for example, other programs report a clock speed of only 621MHz. The basic overclocking functions still operate properly, although increasing clock speeds is still possible.

Voltage Tweaking via ATiTool

On certain video cards, ATiTool has the ability to increase the voltage being fed to the GPU and RAM. However, this capability is not yet enabled on the GeForce 8800GTS.

Stream Processors

The 8800GTS features 96 stream processors, which are unified processors that handle the functionality that both pixel processors and vertex shaders handled on previous video cards. On the GTS, these processors run at a clock speed of 1200MHz. At this time, with most overclocking methods, this clock speed is linked to the GPU speed, so any overclocking adjustments to the GPU speed affects the stream processor speed as well. This link might negatively impact overclocking if either the GPU or the stream processors hit a clock speed ceiling before the other does. However, RivaTuner is able to independently overclock the GPU and Stream Processors, making it the ideal overclocking application for both the 8800GTS and 8800GTX, or 8800GT.

Unlocking Additional Pixel Pipelines

One of the primary differences between the 8800GTS and the GTX is the GTX features 128 stream processors, while the GTS has a number of these disabled, leaving it with only 96. At this time, it is unknown if the additional stream processors can be enabled on the GTS.

Stability testing

Once an overclock is set via nTune, ATiTool or any other program, stability should be tested via a torture test. Ideally, the video card should be exposed to an extended period of stress via a game or looped demo or benchmark. 3dMark is a viable option for stress testing a video card, as is RTHDRIBL (Real Time High Definition Range Image-Based Lighting). RTHDRIBL will continually loop a 3d demo in a window or full-screen until stopped, providing an ideal testing method. Note: the idea here is to actually stress the video card, so running an old game engine or even RTHDRIBL in a small window may not provide enough challenge to determine if the overclock is stable. The ideal scenario is a high-resolution, modern 3D engine with high levels of antialiasing or anisotropic filtering in order to fully stress the video card. If using RTHDRIBL, resize the window until it takes up as much of the screen as possible or run it in full-screen mode. NOTE: Due to the power-saving functionality built into modern video cards, it is likely that the overclocked settings only are applied when a full-screen 3D application is running. In other words, when RTHDRIBL is running in a window, the GPU and RAM will remain at their stock 2D settings. In order to adequately stress test when using RTHDRIBL, you should run RTHDRIBL in full-screen mode to ensure the overclocked settings are applied.

What makes an overclock unstable?

A video card will show signs of excessive overclocking by either showing artifacts in a 3D application or by crashing altogether. One of the easiest ways to test for artifacts is to run 3DMark a handful of times and watch for any abnormalities displayed by the video card.

Overclocking Benchmark Results

These tests will be performed on a system that contains the following relevant hardware and software:

• Intel Core 2 Duo E6600 at 3.2GHz
• 2GB OCZ DDR2-800 at 712MHz dual channel
• eVGA GeForce 8800 GTS 320MB
• Windows XP Media Center Edition
• 3DMark 06

The table below will detail the increase in 3DMark score that resulted from overclocking the above mentioned system: Unfortunately, the roughly 20% overclocks of the GPU and RAM speeds did not translate into a 20% increase in 3DMark score, which indicates there is another potential bottleneck in this configuration. It is possible that the relatively "modest" 320MB of video RAM in this case is hampering the card's performance in the 3DMark 06 benchmark.

The table above is an 8800GTS overclocking database of sorts. Results have been compiled from around the web. Where available, the exact model of the card has been included. In addition, both "stable" as well as "maximum" overclocked speeds have been included. The Stable clock speeds are indicative of speeds that can withstand long gaming sessions or 3DMark runs, or show zero artifacts in ATITool. The "maximum" speeds might indicate the highest speed a card can complete a single 3DMark run, for example.

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