hello folks,

I am planning to upgrade my PC's ram. currently the ram I have is 2x256MB=512MB/133MHz (DDR266) - DDR SDRAM, PC-2100.

My guess is that it has 184 Pins.

I would like to get a DDR2 with 667MHz, 240 pin. Is it possible, since pins don't match. Do they have to match? (there are 3 slots on motherboard for DDR)

regards

I guess it is possible, since there are no restrictions placed from the vendor, as long as you have enough slots, and the motherboard supports this type of RAM, plus I haven't heard so far for pin mismatch issue. Certainly, there're more experienced people here than me, so please correct me if I'm wrong.

Yes the pins do have to match, and the base speed also has to match.
Take one of the pieces of memory with you to a knowledgeable dealer and make sure you get the right part.
You may be able to use 333 memory with 266 memory, as the base speed is 133, (multiplier of 2.5 and 2 respectively). 400 memory definitely will not work.
Also check the motherboard manual, or the manufactures web site to find out the maximum memory module size supported. There may also be a list of qualified memory vendors and part numbers there as well.

all right jgt, I understand it..

so if I want to fill the last empty slot in my motherboard for RAM with a 400 MHz one, it won't work, since the other 2 slots have 133 MHz ram.

What about, if I totally get rid of the 2 x 133MHz existing rams from the motherboard, and get new 184 pin PC-2100 but 400 MHz. this way there will be no conflict. would that work?

That may work, but, make sure you can return the memory if it doesn't.