CertiGuide to A+ (A+ 4 Real)  9  Chapter 9: Graphic Cards       9  Card Components, Modes and Architecture

Upgrading, Troubleshooting, and Common Problems 1 Chapter 10: The Small Computer System Interface, SCSI

Here are some of the more common BIOS settings related to video and how they are used:

• Video Bios Shadow: Video BIOS shadowing copies the VESA Bios from the video card's ROM (slow, REFERENCE ROM) to RAM, where access is much faster. This results in a performance increase, as the BIOS is in constant use.
  
  
• Assign IRQ to VGA: As the setting description implies, this assigns an IRQ to the VGA interrupt. This should always be enabled to allow operating systems to interact with the card.
  
  
• VGA Palette Snoop: This enables a device to watch the VGA palette to see if it changes. This was most commonly used with old ISA video cards that provided TV tuner capabilities. For modern PCI and AGP cards, this should be disabled.
  
  
• AGP Aperture: This defines how much system RAM the AGP bus has access to. An ideal size is between 1/3 to ½ system RAM - graphics cards with more onboard RAM can use a smaller value here
  
  
• AGP Turbo: This is a fancy name for "Write Allocation Mode”. Very few machines can actually operate correctly with this enabled, so as a rule it should be disabled.
  
  
• VGA Boot From: As the description implies, this controls where the VGA BIOS is sourced. Normally the options are AGP or PCI, and should be set to the location of the graphics card.

Upgrading, Troubleshooting, and Common Problems 1 Chapter 10: The Small Computer System Interface, SCSI