Issues with incompatible RAM modules

Hello, I have an old system and I need to buy some RAM (DDR2).

Current RAM:
1x1 GB Transcend 533 MHz CAS L = 4

Planning to buy:
1x2 GB Transcend 667 MHz CAS L = 5

Both require the same voltage (1.8v) and according to the motherboard manual both should be compatible individually. The manual also states that CL of the 533 Mhz and 667 Mhz memory modules should be 4 and 5 respectively.

I assume that both will work together and that the 667 Mhz memory will work with the specifications of the 533 Mhz memory module. Then, this creates a problem as the 667 Mhz memory will have to work with CL4.

Is is time to retire the old RAM or will they work together?
5 answers Last reply Best Answer
More about issues incompatible modules
  1. Best answer
    533 MHz at CAS 4 is basically the same as 667 MHz at CAS 5. The new module should work fine at 533 MHz and CAS 4.
  2. Best answer selected by Healy.
  3. Thanks for the reply. I really appreciate it.

    Just to make sure, do you think that the motherboard manual must be referring to the 667 Mhz to be used at CL 5 only when it is to be used individually? This is copy-pasted from the manual:

    DIMM Type and Timings listed below:
    Type Timing
    DDR2-667 5-5-5 only
    DDR2-533 4-4-4 only
  4. It means that the default settings are as stated in the manual. In other words, when running at 667 Mhz, it uses 5-5-5-x timings and at 533 Mhz it uses 4-4-4-y timings. You can see all available timings for each memory module in CPU-Z, SPD tab.
  5. GhislainG, thank you again.
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