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How to Set your Memory Timing in BIOS

The BIOS on your motherboard offer numerous settings to optimize your memory. These settings modify RAM functions that, while basic in nature, are often given widely different names. There are five basic settings that if set correctly can help optimize your memory. We'll briefly explain the options. We've also included examples of what the settings might be called in different BIOS versions.

NOTE: Not all BIOS menus offer all these settings.

  1. tCL - CAS Latency (also labeled as CAS Latency Time, CAS Timing Delay) The number of clock cycles that pass from the column being addressed to the data arriving in the output register. The memory manufacturer lists the best possible setting as the CL rating.
  2. tRCD - RAS to CAS Delay (also labeled as Active to CMD) Number of clock cycles that pass between the row address being determined and the column address being sent out. Setting this value to two clock cycles can enhance performance by up to four percent.
  3. tRP - RAS Precharge Time (also labeled as RAS Precharge, Precharge to active) Number of clock cycles needed to precharge the circuits so that the row address can be determined.
  4. tRAS - Row Active Time (also labeled as Active to Precharge Delay, Row Active Delay, Row Precharge Delay) Delay that results when two different rows in a memory chip are addressed one after another.
  5. CMD - Command Rate (also labeled as CMD Rate) Number of clock cycles needed to address the memory module and the memory chip with the desired data zone. If your memory banks are full to capacity, you will have to raise this rate to two, resulting in a considerable drop in performance.

Memory timings are usually in the following order:

tCL - tRCD - tRP - tRAS - CMD

For example, our PDC1G3200LLK has a timing of 2-3-2-5-t1. This translates to the following:
tCL = 2   tRCD = 3   tRP = 2   tRAS = 5   CMD = 1


We've also included examples of what the settings might be called in different BIOS versions. Please note that not all BIOS menus offer all the settings It is recommended that customers using our Patriot Extreme Performance or Dual Channel memory set their BIOS to the settings specified for their memory.