RAM Comparison...

[MASTOURA]

Can someone explain if the following logic is correct?

128 MB of 266 Mhz DDR

equals

256 MB of 133 Mhz DRAM

ANd if the above is correct, how many DRAMs is a stick of 128 MB at 800Mhz Rimm is worth?
This ofcourse in the case we can make a comparison...

Thanks!

M.

[daveleau]

No that is not correct. Sorry.

128MB is the amount of memory and PC133 or PC2100 is the speed of the memory.

256MB is trwice as much memory at every speed.

PC133 is slower than PC2100 (DDR) at any amount.

There is no such thing as 266MHz DDR, it is called PC2100. I am not up on the specs so I will leave that to someone else for now.

RDRAM is the most expenisive ram to be on the brink of extinction, as Intel is aboutt to drop support od it in leui of DDR.

Dave

[This message has been edited by daveleau (edited 07-04-2001).]

[otheos]

Like dave said:

PC2100 is DDR SDRAM. the 2100 (or 1600 for PC1600) is the bandwidth each of the new architecture offers. PC2400 (latest) offers 2.4GB/s bandwidth so you can say that it's "faster" than PC2100 and PC1600. This memory runs at Double Data Rate of 133MHz bus = 266Mhz.

PC133 is SDR SDRAM and it's called PC133 from the speed of the bus it runs on. PC133 runs on 133Mhz, PC100 on 100Mhz and PC66 (older Celerons) on 66Mhz. The higher the Mhz the higher the bandwidth offered so you could say PC133 is "faster" than PC100 etc.

Since the Bus is 64bit wide, the maximum bandwidth is 64*freq in Mhz
PC66=64*66=4224Mbits/sec=4244/8 Mbytes/sec=528 MB/s

PC100=64*100/8=800MB/s
PC133=1064MB/s

But this is the bandwidth not the speed!! If you use an application that does not saturate the bandwidth of neither PC100, nor PC133, then if the two memory sticks, one PC100 and one PC133 were used that had the same latency, they would performe identically. If the PC100 had a lower latency it would even be FASTER!

Today though, 800MB/s and 1064MB/s are quite different in most apps, so PC100 will limit the performance. However if pure speed is what you're after, you should get some low latency sticks. This is identified by the CAS2 or CAS3 parameter (also called CL2 or CL3). CL2 is faster than CL3 (but more expensive too). This is true for DDR memory. PC2100 comes in CAS2.5 and CAS2.

For Rambus..... don't waste money on it.