Is PC 133 Mhz Memory Module compatible with 100 Mh

  Rogmur 23:02 06 Nov 05

Hi Helproom Forum Members

I have two PC 133 Mhz (SDRAM) Memory Modules,
which I would very much like to use in my aging
Dell Dimension 550 (PIII).

However, the PC is fitted with one module of 128MB of SDRAM which is PC 100Mhz.

Is 133Mhz backwards compatible with 100Mhz?

Many thanks in advance


  alan227 23:08 06 Nov 05


  GaT7 23:11 06 Nov 05

"Is 133Mhz backwards compatible with 100Mhz?" - Yes, no problem, but they (all the RAM) will work at the slower 100Mhz speed. G

  Bandy 23:13 06 Nov 05

The answer is normally Yes - But

The problem is more likely to be the way in which the memory is made ie the size of the chips, although not physically but the way the memory is handled.

I've bought a number of sticks recently and some worked in old machines and some not - because of their type not speed.

If you need to be sure I would suggest Crucial who will supply memory guaranteed to work on the machine.

Since you have the modules however I would suggest that you try them. Its very unlikely that you will harm them or the machine

Good Luck

  Rogmur 23:19 06 Nov 05

Thanks all, will give it a go,
I am relieved to hear it won't harm my pc.

Kind regards


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