Chapter 14: Overclocking Video Adapters and Hard Drives

The reliability and performance of hard drives and video adapters depends significantly on the modes in which they are used.

The working modes of hard disks and video adapters depend on the frequency of the buses to which these devices are connected, along with their controllers. For hard disks, the frequency modes are determined by the PCI bus. For a video adapter this might be either the AGP bus or PCI bus, depending on the device type. Notice that for motherboards manufactured several years ago and oriented towards 486 or 386 processors, these might be other buses, such as the VLB, MCA, ISA, or EISA.

The frequencies of buses such as PCI, AGP, and, quite often, their legacy predecessors, depend on the frequency of the processor's front side bus (GTL+/AGTL+, Alpha EV6). Usually, the frequencies of the PCI and AGP buses are set by dividing the FSB frequency. An example provided below lists the most commonly used FSB, AGP, and PCI frequencies often implemented in motherboards.

Here are the most common frequencies implemented in motherboards with the i440BX chipset:

The architecture of most motherboards provides tools allowing you to correct the AGP and PCI frequencies not only by changing the FSB frequency, but also by changing the appropriate bus frequency multipliers. This can be achieved either by setting special parameters in BIOS Setup or with special switches or jumpers on the motherboard. Changing the bus frequency enables you to select the optimal mode for the devices managed by the corresponding buses.

The standard software and hardware tools generally don't provide special capabilities for overclocking hard drives. However, hard drive performance depends on the frequency of the PCI bus to which they are connected via the respective controllers. The existence of such dependence is illustrated by the results produced by testing a PC in the overclocking mode with the WinCheckIt program (v2.03) at various values of the FSB frequency. The FSB frequency determines the PCI frequency, and via this frequency it influences the hard drive's performance. The table provided below shows the results of performance evaluation for the hard drive when using the WinCheckIt (v2.03) program at various values of the PCI bus frequency.

Hard disk performance for different PCI frequency values obtained by WinCheckIt program:

Hard disk performance for different PCI frequency values according to the data obtained by WinMark 99 test:

Notice that not all hard drives can satisfactorily tolerate overclocking via increase of the bus frequency. For some drives you will see a performance gain, while for other drives you may even notice a performance degradation. The results of such overclocking depend both on the device type and on the specific device instance. Most modern hard drives with a capacity larger than 10 GB will work well at overclocking frequencies (for example, 42 MHz or even higher), provided that you are using high quality motherboards. If you are using smaller hard disks (less than 1 GB), such modes are normally impossible, because the technologies and components of such devices are not as advanced as the ones used in newer hard disks. However, despite the fact that most high-capacity hard disks are able to function at high PCI frequencies, it is not recommended that you set the bus frequency higher than 40 MHz. Such modes increase the probability of failure when performing data reads and writes (and, consequently, the risk of data loss). Besides this, they make the temperature mode worse for both the electronic and mechanical components of the hard disk. Note that most high-performance disks with a large amount of built-in cache memory (up to 2 MB) and a high rotation speed (7200 RPM, for example) often require additional cooling, even in nominal modes. This is especially true when using several such devices within a small system unit along with other high-performance components characterized by excessive heat emission. If this is the case, it is advisable to use adequate cooling facilities not only for the processor or video adapter, but also for the hard drive(s). Unfortunately, this can't always be implemented. Thus, the limitations caused by temperature modes and insufficient speed parameters of the electronic and mechanical components of hard drives are the most important factors preventing hard disks from being overclocked.

Modern high-performance video adapters based on advanced components tolerate more significant changes in their respective buses (AGP) as compared to hard disks. However, they also are not always stable at the high frequencies obtained as a result of processor overclocking. The table provided above illustrates this fact rather well. As with hard disks, the influence of increased AGP frequencies on the video output performance can be traced when analyzing practical overclocking examples.

Somewhat increasing the AGP frequency provides performance gain when processing video output. Furthermore, increasing the frequency of this bus also increases the bandwidth, which, in turn, increases the data transfer rate. As a result, the video subsystem performance increases proportionally to the increase of its bus speed. On the other hand, certain specific architecture improvements and frequency characteristics of the electronic components that provide the basis for a modern video adapter tolerate a significant increase of the AGP frequency. For example, some devices using modern high-performance components and the most advanced technologies are capable of working at frequencies up to 100 MHz, which is approximately 50% larger than the nominal value of 66 MHz, standard for the AGP bus.

However, the capabilities of this overclocking method are also limited. As a rule, the limits of the growth in AGP frequency are applicable only to individual high-quality instances of video adapters. Normally, these values are somewhat lower. Furthermore, heightening the possible video adapter frequency and performance is limited by individual components whose functional capabilities don't allow them to work at higher frequencies. If this is so, the potential capabilities of other elements that can tolerate overclocking will not be implemented.

A significant and, more importantly, well-balanced increase of the video adapter's speed can be achieved using specialized software utilities. Usually, such tools allow you to perform selective overclocking of the chipset and video memory, which together provide the basis for the video adapter. Overclocking capabilities intended for increasing the video subsystem performance can be supplemented by increasing the video adapter bus (AGP bus).

The PowerStrip utility developed by EnTech Taiwan (http://entechtaiwan.com) can be considered an example of universal software intended for video subsystem overclocking.

This utility provides tools for changing the working modes of the video adapter and monitor. The range in which you can change the monitor's vertical sweep (refresh frequency) encompasses up to 200 Hz, and is limited only by the capabilities of the video adapter and the monitor itself. Besides controlling this frequency, PowerStrip allows you to change the frequencies of the video chipsets and video memory, and enables you to test video adapters.

PowerStrip supports video chipsets from the following vendors 3Dfx, 3Dlabs, ATi, Cirrus Logic, Intel, nVidia, Matrox, S3, SiS, Trident, Tseng Labs, etc. The list of supported chipsets includes, for example ATi Rage II Pro, CL GD543x/544x/546x, i740, Matrox G100, Permedia, PowerVR, Riva128/128ZX, S3 Vision86x, S3 Vision968, S3 Trio32/64, S3 TrioV+, S3 TrioV2/DX, S3 TrioV2/GX, S3 Trio3D, S3 ViRGE, S3 ViRGE/VX, S3 ViRGE/DX, S3 ViRGE/GX, S3 ViRGE/GX2, SiS 6326, Trident ProVidia 9685, ET6000, ET6100 and many more.

This program works under Windows 9x and Windows NT, and allows you to control the functioning of practically all models of monitors, including ones provided by such well-known vendors as Hitachi, MAG, Mitsubishi, NEC, Nokia, Panasonic, Philips, Sony, ViewSonic, etc.

There are other universal programs that support a large variety of video adapters and monitors. However, most vendors provide special software tools and utilities along with their products. Besides testing and optimal tuning, this software provides tools for optimizing the video chipset and video memory. Quite often, such tools can be downloaded from the Internet or obtained from firms specializing in selling and supporting video adapters.

Besides commercial software intended to control the operating modes of your video subsystem, which is generally developed by video adapter manufacturers, there are lots of shareware and freeware utilities developed by overclocking enthusiasts. There are tons of such software on the Internet. Some Web addresses, where you can find such programs and support information, are provided in Chapter 20.

To conclude this chapter, let us consider an example of overclocking the Matrox Millennium G200 video adapter. Overclocking in this example was accomplished using the standard motherboard hardware.

• Test: 3D WinBench 98 (800×600×32)

• Motherboard: Asus P2B-S

• RAM: 128 MB CAS2 SDRAM

• Video adapter: Matrox Millennium G200, AGP, 250 MHz RAMDAC, 8 MB SGRAM, 128 MB Graphics Aperture Size

• Processor: Intel Celeron 300A

• Overclocking parameters: increasing the bus frequency to 75/83/103 MHz

• OS: Windows 98

The overclocking of the components was performed by increasing the FSB starting from the standard value (66 MHz) and going up to 103 MHz. The resulting performance gain of the video subsystem is illustrated by Figs. 14.1-14.3.

Fig. 14.1. Test results from 3d WinBench 98/3D Processing

Fig. 14.2. Test results from 3D WinBench 98/3D Scene

Fig. 14.3. Test results from 3D WinBench 98/3D WinMark