Parameters of Memory Overclocking. Part III

System Memory Multiplier (FSB/Memory Ratio)

It determines the ratio (multiplier) between FSB frequency (BCLK) and memory frequency.

Possible values:

  • Auto – the ratio between FSB frequency (BCLK) and memory frequency is set automatically according to SPD data;
  • the ratio (for example, 1:1, 1:2, 3:2, 5:4) or the multiplier (2, 2.5, 2.66, 3.00, 3.33, 4.00 and others) which determines the connection between FSB frequency (BCLK) and memory frequency. A particular set of values depends on the type of chipset and motherboards model.

Manual multiplier setting is used for overclocking and in this case the multiplier (ratio) in order not to reach unsustainable levels when a base frequency is raised. You can control an actual value of memory frequency with the help of information parameter “Memory Frequency” or diagnostic utilities, for example CPU-Z ( or EVEREST.

CAS# Latency (tCL, DRAM CAS# Latency)

This parameter sets the delays between the toning of the column sample (CAS#) and beginning of data transmission.

Possible values of this parameter depend on the type of used modules and motherboard model. A range adjustment for DDR memory may be from 1,5 to 3 cycles, for DDR2 – from 3 to 7 cycles, for DDR3 – from 4 to 15 cycles. If the value “CAS# Latency” is decreased, the memory operation will accelerate, but not all the modules can operate stably within the low delays.

RAS# to CAS# Delay (tRCD, DRAM RAS-to-CAS Delay)

This parameter modifies the time of delay between the toning of the line sample (RAS#) and the toning of the column sample (CAS#).

A range adjustment depends on the motherboard model and may be from 1 to 15 cycles. The less value, the faster access to the cell is. But too low values will lead to unstable memory operation.

RAS# Precharge (tRP, DRAM RAS# Precharge, SDRAM RAS# Precharge, Row Precharge Time)

This parameter sets the minimum permissible time to recharge the line after it was closed.

Possible values – from 1 to 15. The memory operates faster with lower values, but too low values may lead to instability.