Different Memory Speeds

By gurpreet ·
Hello Friends,

I have 2 laptops, Dell (E1505) and Toshiba (U205-S505. Both of them have the FSB of 667 MHZ. However, the ram on both the laptops is 533 MHZ, 512 MB x 2 (1GB).

Now, I am thinking of upgrading the memory on both the laptops by buying 2 modules of 1 GB each, 667 MHZ, PC2-5300. Hence, each laptop will then have one 512 MB (533 MHZ) and one 1 GB (667 MHZ).

So, I would like to take some knowledge regarding the compatibility of using different memory speed on the same motherboard. Will this create any problem to use 533 MHZ in 1 memory slot and 667 MHZ on the other one?

Please let me know.

Thanks a bunch!


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The faster memory will revert

by OldER Mycroft In reply to Different Memory Speeds

The faster memory will only be able to run at the speed of the slower memory stick, if it runs at all.

Better to run matched pairs in any computer situation.

You could put the 2 1GB sticks in one laptop and install the other 2 512MB sticks in the other laptop. That would be the most capable use of your available resources.

Any increase in speed between the two laptops is more likly to be due to the 2GB compared to the 1GB, as opposed to the greater speed of each memory installation.

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The RAM will run at the speed of the Slowest Stick available.

by HAL 9000 Moderator In reply to Different Memory Speeds

Also with Modern Intel CPU's while the FSB may be measured at a certain speed you need 2 sticks of RAM to drive it at this speed as these are Dual Input and each receive a data feed through a RAM channel. So if you have 1 stick of RAM present you only run at 50% of the possible CPU Speed as half the FSB is not available to the CPU.

While AMD CPU's work a bit differently they also benefit from having 2 sticks of RAM to feed them as they work better than with just 1 stick but no matter what I would still consider using the same size RAM so that you don't hit any timing issues or other RAM Issues.

With XP unless you are pushing it with some Graphic Rendering Application 1 GIG works quite nicely and while 2 GIG is nice in some cases it actually slows the computer down depending on the CPU's architecture. Also fitting different size RAM Sticks to a computer of any form particularly NB's will give you more of a performance hit than improvement.

If you need more than 1 GIG of RAM replace all of the RAM and sell off the existing RAM on a place like E-Bay to recover some money and minimise the costs of buying 4 X 1 GIG RAM sticks.

Also first make sure that the computers can actually hold 1 GIG RAM sticks as quite a few NB's have a upper limit of 512 MEG per RAM Slot making the unit max RAM of 1 GIG. It's only since the Dual Core Intel's have become available that 1 GIG RAM Sticks have become possible to use in these machines.


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