Ram with 2 different bus speeds

By jim.turnbull7 ·
I recently got a free Gb of DDR PC2700, which is the recommended speed. I'm using that with a Gb stick of PC3200, which my computer will also support. My computer has been acting pretty strangly. I was just wondering this was conincidental or using ram with two diffent bus speeds will cause undesired results

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Under ideal conditions

by OH Smeg Moderator In reply to Ram with 2 different bus ...

The system will revert to the slower RAM Speed and just be slower.

However in Real Life this doesn't often happen and the system becomes unstable. You get Timing Issues with different speed RAM which can manifest themselves in numerous ways. So I would say that you should remove the slower RAM Stick and either go with the original or buy another stick of the same speed as the original to get best results.

If you have a M'Board that supports Dual Chanel RAM you really do need identical RAM Sticks in each socket of the pair to get best results.


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Slow RAM in First Socket

by TheChas In reply to Ram with 2 different bus ...

Generally speaking, I try to use matched sets of RAM in any PC I set up. It just works better.

In your situation, installing the slower speed RAM in the first or lowest numbered slot will usually provide the best chance of everything working well.

You may still need to go into BIOS setup and tweak the RAM settings.

1 thing I have noticed is that faster RAM often has a higher CAS latency specification than slower RAM does. In order to get the system to run stable, you may need to adjust the RAM timing so slow as to negate the performance improvement of the additional RAM.

Like OH Smeg, I recommend that you buy another DIMM that matches your faster RAM.


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Voltage is Key

by willcomp In reply to Ram with 2 different bus ...

Usually the faster RAM will step down without problems -- apparent since your system specs DDR333 memory. The reduced speed decreases latency also, so both sticks should be close if they are "normal" memory.

Performance memory usually requires higher voltages for stable operation. If modules are voltage mismatched, one will be at either higher or lower voltage than required. The standard voltage for DDR RAM is 2.5VDC.

Do as previously suggested and install DDR333 module in first slot after verifying that both modules are 2.5V memory.

You can also test using Memtest 86+.

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