ECS SF2/648FX Manual page 40

DRAM Clock/Timing Control
Scroll to this item and press <Enter> to view the following screen:
DRAM Timing Control (By SPD)
Enables you to select the CAS latency time in HCLKs of 2, 2.5, or 3. The
value is set at the factory depending on the DRAM installed. Do not change
the values in this field unless you change specifications of the installed DRAM
or the installed CPU.
DRAM CAS LATENCY (2.5T)
This item controls the timing delay (in clock cycles) before the DRAM starts a
read command after receiving it.
RAS Active Time (tRAS) (6T)
This item allows you to set the amount of time a RAS can be kept open for
multiple accesses. High figures will improve performance.
RAS Precharge Time (tRP) (3T)
This is the duration of the time interval during which the Row Address Strobe
signal to a DRAM is held low during normal Read and Write Cycles. This is
the minimum interval between completing one read or write and starting an-
other from the same (non-page mode) DRAM. Techniques such as memory
interleaving, or use of Page Mode DRAM are often used to avoid this delay.
Some chipsets require this parameter in order to set up the memory configura-
tion properly. The RAS Precharge value is typically about the same as the
RAM Access (data read/write) time.
RAS to CAS Delay (tRCD) (3T)
This is the amount of time a CAS is performed after a RAS. The lower the
better, but some DRAM does not support low figures.
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