Buying Memory

I just went to buy some memory and saw something I have not noticed in the past. The memory speed calculation is pretty interesting. I of course had to find the fastest memory before I purchased. What amazed me was the difference from brand to brand and even more interesting is that some brands do not even list their speeds! I endedd up buying two more gigabytes ram giving me a total of 3GB. It had what looks like the best CAS latency value of 2-3-2-5.

These are relatively important timing terms:

  1. tRP – The time required to switch internal memory banks. (RAS Precharge)
  2. tRCD – The time required between /RAS (Row Address Select) and /CAS (Column Address Select) access.
  3. tAC – The amount of time necessary to “prepare” for the next output in burst mode.
  4. tCAC – The Column Access Time.
  5. tCL – (or CL) CAS Latency.
  6. tCLK – The Length of a Clock Cycle.
  7. RAS – Row Address Strobe or Row Address Select.
  8. CAS – Column Address Strobe or Column Address Select.
  9. Read Cycle Time – The time required to make data ready by the next clock cycle in burst mode.

Note #1: tRAC (Random Access Time) is calculated as tRCD + tCAC = tRAC
Note #2: RAS and CAS normally appear in technical manuals with an over-line as in RAS or CAS.

Reference Link: link here

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