Asus P4B266-E - Manual (Page 90)

4-20 Chapter 4: BIOS Setup
Delayed Transaction [Disabled]
When set to [Enabled], this feature frees the PCI bus when the CPU is
accessing 8-bit ISA cards. This process normally consumes about 50-60
PCI clocks without PCI delayed transaction. Set this field to [Disabled]
when using ISA cards that are not PCI 2.1 compliant. Configuration
options: [Enabled] [Disabled]
Onboard PCI IDE [Both]
This field allows you to enable either the primary IDE channel or
secondary IDE channel, or both. You can also set both channels to
[Disabled]. Configuration options: [Both] [Primary] [Secondary] [Disabled]