What is the difference between 128Meg x 64 & 256Meg x 64 PC-5300 memory

[KARATEJOHN]

Looking to upgrade a Lenovo Thinkpad Z61e

 

[photonboy]

AFAIK it amounts to the same thing. One has more 2X the number of chips but HALF the memory on each chip.

If you can't get the EXACT same model number (i.e. to go from 4GB to 8GB), then make sure the new memory:

a) is rated for the same FREQUENCY
b) has the same CAS rating

For example, DDR3 1600MHz CAS9 (and obviously is the proper memory TYPE, SODIMM or whatever for your laptop)

 

[Shaun o]

The first poster is spot on.
Just one more thing to add. back in the old days you had to watch what type of memory sticks you bought , because some memory slots on laptops or motherboards would only take single sided populated boards. for example in the case above a 128mb memory chip you would need more of so it would be likely that both sides of the board have memory chips on.

Where as one with 256 memory chips on only requires one side of the memory stick to be populated with chips.

It depends on the age of the laptop, but if it`s DDR3 there is no problem at all.