Video BIOS Settings
Many manufacturers, such as AOpen, are beginning to allow access to the Video BIOS as well as the System BIOS, to allow the use of various display devices and to extract maximum performance from the more complex chipsets available, even down to adjusting the speed of the fan on the video card. In AOpenís case, at least, you get to them by pressing the Insert key as the machine starts. These are becoming more relevant as nVidia brings its own motherboard chipset more into circulation, which contains its own high speed, quality graphics
sub-system. Otherwise, you may find these settings available through software supplied with your card.
AGP 4x Drive Strength
See also AGP Driving Control, below. You can set whether the drive control is manual or done by the chipset (auto). The choices in manual mode are made under AGP Drive Strength P or N Ctrl, below.
AGP Drive Strength P or N Ctrl
This setting appears when manual is selected under AGP 4x Drive Strength, above. The figures are in hex, and higher values represent stronger signals, which is what you need when overclocking, so this is only indirectly related to performance. Both ranges are from 0-Fh, but P covers the first part, N the second, of the values concerned, so the actual range is 00-FFh (that is, 0-255). C4 is a typical default.
AGP Driving Control
Allows overriding of the automatic settings for more precise control when overclocking. Choices are manual and auto. Used in conjunction with......
AGP Driving Value
See also AGP Drive Strength P or N Ctrl, above. This only works if AGP Driving Control (above) is set to Manual. It concerns the signal strength of the AGP bus, with higher values representing stronger signals, making it useful for stability when overclocking, so it only affects performance indirectly (be careful about your card). The range of 00-FF means 0-255 in decimal values, with a typical default being DA (218). However, for NVIDIA GeForce2-based cards, try EA (234).
AGP Comp. Driving
Used by AMI BIOS's to adjust the AGP driving force. Selecting Manual gives you another setting, Manual AGP Comp. Driving,
below. Auto is best for safety.
Manual AGP Comp. Driving
AGP Fast Write Transaction
This allows data to be sent directly from the corelogic (i.e. chipset) to the AGP master (graphics chip) instead of keeping a copy in system memory and making the AGP master fetch it. In other words, it creates a short cut between the AGP chipset and graphics memory, and leaves system memory out of the loop. Enabled is best for performance, and probably only works with 4x cards anyway.
AGP fast Write
See above (AMI BIOS).
AGPCLK/CPU FSB CLK
The relative speeds against each other of AGP and CPU bus clocks. 1/1 means that the AGP is running at the same speed (for older processors). 1/2 means that the FSB is at 133 MHz, so AGP can use its standard speed of 66 MHz, but you can stretch it to 75, or even 83 in some cases. For best performance, the AGP figure should be easily divisible into the higher speed.
AGP Transfer Mode
Seems to override the automatic selection of 1x, 2x or 4x.
AGP Master 1 WS Read
Implements a single delay when reading from the AGP Bus. Normally, two wait states are used, allowing for greater stability, but check with your motherboard manufacturer to see if they have already implemented a Master latency of zero, in which case the lowest reading here of 1 will reduce performance.
AGP Master 1 WS Write
As above, but for writes.
AGP Sideband Support
Enable or disable. AGP Sideband Addressing is a transfer mechanism allowing the card to send and receive at the same time, by using a second bus for addresses and commands to the graphics processor, so the data can flow as fast as it can over the AGP bus. It may decrease stability, however, and cause crashes on the Savage3D, due to the design of some motherboards resulting in glitches on strobes (in fact, you need support on the motherboard, graphics card and drivers). Try using Pipeline Transfer instead - performance will probably be the same.
AGP Read Synchronization
Enabled is best for performance.