Asus P4B266-C - Manual (Page 80)

4-18 Chapter 4: BIOS Setup
4.4.1 Chip Configuration
The DDR SDRAM CAS Latency parameter appears only when you set
the SDRAM Configuration to [User Defined].
SDRAM RAS to CAS Delay [3T]
This item controls the latency between the DDR SDRAM active command
and the read/write command.
The DDR SDRAM RAS to CAS Delay parameter appears only when
you set the SDRAM Configuration to [User Defined].
SDRAM Configuration [By SPD]
This parameter allows you to set the optimal timings for items 2–5,
depending on the memory modules that you are using. The default setting
is [By SPD], which configures items 2–5 by reading the contents in the
SPD (Serial Presence Detect) device. The EEPROM on the memory
module stores critical information about the module, such as memory type,
size, speed, voltage interface, and module banks.
Configuration options: [User Defined] [By SPD]
SDRAM CAS Latency [2.5T]
This item controls the latency between the SDRAM read command and
the time the data actually becomes available.