Intel AIMB-253 - Manual (Page 48)

AIMB-253 User Manual 38
DRAM Timing Selectable
Selects whether DRAM timing is controlled by the SPD (Serial Presence
Detect) EEPROM on the DRAM module. Setting to [By SPD] enables
DRAM timing to be determined automatically by BIOS based on the con-
figurations on the SPD. Selecting [Manual] allows users to configure the
following fields manually.
CAS Latency Time
This controls the timing delay (in clock cycles) before SDRAM starts a
read command after receiving it. Smaller clocks increase system perfor-
mance while bigger clocks provide more stable system performance.
DRAM RAS# to CAS# Delay
This field allows you to set the number of cycles for a timing delay
between the CAS and RAS strobe signals, used when DRAM is written
to, read from or refreshed. Fast speed offers faster performance while
slow speed offers more stable performance.
DRAM RAS# Precharge
This item controls the number of cycles for Row Address Strobe (RAS)
to be allowed to precharge. If insufficient time is allowed for the RAS to
accumulate its charge before DRAM refresh, refresh may be incomplete
and DRAM may fail to retain data. This item applies only when synchro-
nous DRAM is installed in the system.
Precharge Delay (tRAS)
The field specifies the idle cycles before precharging an idle bank.
System Memory Frequency
Use this item to configure the clock frequency of the installed DRAMs.
**VGA Setting**
The following items allow you to configure the VGA settings of the sys-
tem.
PEG/Onchip VGA Control
This setting allows you to select whether to use the onchip graphics pro-
cessor or the PCI Express card.
When set to [Onchip VGA], the motherboard boots up using the onboard
graphics processor, even when a PCI Express graphics card is installed.
When set to [PEG Port], the motherboard boots up using the PCI Express
graphics card, if one is installed. Otherwise, it defaults to the onboard
graphics processor.