Diff Between SDRAM and DDR???

[teabgs]

Hey all. I was just wondering what the technical differences between SDRAM and DDR are. Feel free to be as simple or as technical as you wish. Also, analogies are good. Thanks everyone!


-Tea

[-=AsukA=-]

DDR-RAM is much faster and much more in with modern "high tech" times...
(in "Pro" computers that is...)

[Beej]

In very simple terms:

Think of a sine wave - you know up down, up down with nice curves and stuff.

SDRAM dan do stuff only when the wave is at the very top.

DDR can do stuff at the top of the wave, and at the bottom. Hence the name, Double Data Rate. It is effectively double the speed od SD RAM at the same MHz.

[mozez]

ddr ram is "double data rate", it has a faster bus, right now most ddr runs at 233 to 266, regular sdram moves at 66, 100, 133, also, you get more bandwidth out of ddr.

[teabgs]

Much appreciate. I thank you all for enlightening me.

[mmcneil]

provided by a friend and guru

DDR processes data sets on alternating sequences, the sine wave analogy was really quite good - it really isn't any faster in actual memory latency, but "potentially" does a better job of keeping up with the processor in providing data. Alas, DDR only reaches its full potential in a hardware architecture that can take advantage of it.

I must say I am suprised Apple hasn't done anything with DDR yet.

On the same subject, slightly different flavor - we are in the process of transitioning all of our mac users to TiBooks. According to some sources, Apple requires CL2 however in the TiBooks we have received to date, it is all CL3 memory installed (the number refers to the latency).

anyone else have more information?

[anshelm]

Unless the processor understands DDR, it won't be able to use it. I don't think the G4 can operate with DDR, so if Apple stuck DDR with a G4, it would treat it as if it was SDRAM. So, unless Apple is able to convince IBM/Motorola to incorporate DDR into the next processor design, they are stuck with SDRAM. Hopefully they have. That's just my two cents.

(A simplified graphic of the sine wave analogy is here: http://jeni-lee.com/anshelm/rants/fsb.html )

[Beej]

I don't know if the processor has anything to do with the use of DDR or not... hmmm, I'd never thought about it. I might take a look.

Assuming, though, that the G4 can handle DDR, it is very surprising Apple hasn't done anything with it.

Because Mac processors are RISC, the use of higher speed RAM will be of even bigger benefit to us than our PC using (ahem) friends.

[anshelm]

Well, one wouldn't normally associate memory type with the processor... but DDR operates on the basis that the prcoessor knows it can send twice per clock tick. Otherwise, the DDR memory would behave like SDRAM, because the processor would send only once per clock tick, negatting the DDR's ability to do double the data transfer rate per clock tick.

[Falleron]

I am pretty sure the G4 cant use DDR Ram. Therefore, until the G5 is out we are stuck with SDRAM.

[evildead]

Ram is on of the major bottle necks in any computer. I have been hopping that Apple would have moved in that direction in th quicksilvers. I got one anyway.. but I was a bit dissapointed.