>>I know that it is the 4200 and the 5300, but that seems to be the only difference. The price is the same. I think they are both compatable with my laptop, so why get one over the other and why no price difference?
>>
>>

>>4GB kit (2GBx2)
>>
>>CT533345    DDR2 PC2-4200 • CL=4 • Unbuffered • NON-ECC • DDR2-533 • 1.8V • 256Meg x 64
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>> 4GB kit (2GBx2)
>>
>>CT533355    DDR2 PC2-5300 • CL=5 • Unbuffered • NON-ECC • DDR2-667 • 1.8V • 256Meg x 64
>>

>
>The 667MHz part gives you higher memory bandwidth (more GB/sec transfer) if your laptop mainboard supports it. If your laptop doesn't support it, you won't see any difference.

But the memory bandwidth is not 25% higher: the latency needed is totally identical, as 4 cycles of 133 is 533 and 5 cycles is 667. Since latency is one of the biggest factors...
>
>Whichever one you go for, make sure it actually is compatible. Laptop memory is usually non-standard, i.e. uses a different size/shape circuit board than standard RAM for ATX-style motherboards. These circuit boards are sometimes manufacturer-specific, especially for laptops that are aimed at being small and light.

AFAIK these differences were much greater at BX-chipset times and SD-RAM. The thing to watch out for is the chipset supporting the RAM size: most laptops cannot work with 2 2GB DDR2 SD-0 sticks, there you are restricted to 2 1GB sticks. Same thing as the intel 945G chipset (which is nearly identical in speed for office/non gaming purposes) does not support 2GB sticks, so even with 4 slots you have a 4GB border you can never jump.
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>Laptops also sometimes have nasty surprises such as having one relatively low capacity stick soldered to the mainboard, and only 1 other slot available for expansion. If you can, open up your laptop and check if the existing RAM is removable and what your expansion capability is.
>
>You might also want to make sure that your laptop can support 4GB RAM, some might only support 2GB max.
Ummph, already wrote the above and was too lazy to delete it after realizing you already mentioned it <bg>

regards

thomas