RIMM Question

[mike511]

A Freind of mine has a dell computer with a p3-800 with rdram. HE is not sure of the speed of his 128 stick and wants to add another 128 meg stick to his system. According to dell, the system can support 600, 700 and 800 mhz rimms. Can he mix and match the different ram speeds? OR does he need to find the exact speed of his rimm before he buys more.

Thanks
MIke

[Starmaster5]

I am not sure, but I would venture to guess he needs to get the same speed of RIMM. Don't hold me to it, but I find it hard to believe that a system could have several RIMMS all running at different speeds for memory. Seems that would cause all sorts of timing problems.

[captpete]

I am unfamiliar with RIMMS. Could you mean DIMMS? The latter come in various sizes, not necessarily speeds, since they are basically only holding divices for memory while the power is on. You can combine various sizes, such as a 64 MB chip and a 128 MB chip. The only limitation to size of RAM is the number of slots you have for chips. Thus a motherboard with three slots would be expandable to 768 MB (three 256 MB chips).

The chips are rated for a speed, the access time it takes for the CPU to receive a value from the RAM chip. It is measured in nanoseconds, such as 60, 70 or 80 ns: the lower the number the better. You can mix chips of various speeds, but they will all operate at the speed of the slowest chip.

[captpete]

Oops, I'm way off on this one. Rambus DRAM uses a proprietary RIMM chip. They use a 16 bit data path rather than the 64 bit of DIMMS and can therefore run at much higher speeds with the narrower bus. They are rated from 400 to 800 MHz. If his Dell is rated at 800 MB per second, I think the chip is a 400 MHz. Don't know if you can mix them. I am out of my league here.