I don't understand DDR SDRAM !?!?!

[NucleusWDS]

Where on earth did someone come up with PC1600 and PC2100 DDR SDRAM from?

What does the number 1600 and 2100 derived from?
I know that PC100 = 100Mhz and PC133 = 133Mhz ... so can some explain what this is all about?

 

[Deeko]

It's the data transfer rate, 1600 MB/S, 2100 MB/S.

 

[NucleusWDS]

Still ... how did they work that out?

If ...
PC100 = 100Mhz does that = 100Mb/s
and also
PC133 = 133Mhz does that = 133Mb/s

Then PC1600 = 1600Mhz? = 1600Mb/s
and
PC2100 = 2100Mhz? = 2100Mb/s

?!?!? I'm all confused ?!?!?

 

[Dulanic]

100Mhz SDRAM=800MB/sec hence DDR (Double Data Rate) is double that... 1600MB/sec
133Mhz SDRAM=1050MB/sec hence DDR is double = 2100MB/sec

DDR is effectively double.... so 133Mhz DDR is equal to 266Mhz... just like DDR Video card... and just like the DDR FSB of Athlon boards. Thats where you get the 200Mhz FSB on Athlon boards... its really 100Mhz but its DDR.

 

[NucleusWDS]

Thankyou for enlightening me

WOW ... Really ?!?!

My PC133 is running @ 1050Mb/s ... WOW now that's FAST !!
Didn't realize what a POWERFUL system I have here

And one more thing ...
So why didn't they call DDR SDRAM ... PC200 and PC266 then ?

 

[pm]

For advertising reasons - they wanted to look impressive next to PC600, PC700 and PC800 Direct RDRAM.

And, no, I'm not joking. That's exactly the reason.

 

[TheMinion]

so, the 200 Mhz FSB is actually 100 DDR? That is interesting. What do you mean by only AMD boards? Also I have never seen DDR memory. Do they fit in typical DIMM slots?

 

[Dulanic]

Its both advertising, and not extremelly far off we might have 200Mhz SDR RAM... so you dont want 2 PC200 ram types... so you make it a different #... bandwith was about the only other # they could use.

And While PC133 is capable of 1050... there is overhead etc.... you wont see 1050... the best you see right now is with the KT133 which can do about 500MB/sec. Althought the KT133A kicks that up to about 650MB/sec I believe was what I saw on some benchmarks.

 

[Dulanic]

Well only AMD boards use the DDR bus.... Intel still uses the SDR bus except with the P4 where they use a QDR bus (Quad Data Rate).

And no DDR RAM does not fit it normal SDRAM slots, you need a MB to support it, and thoose are just starting to come out.

 

[TheMinion]

ahh. thanks. i am thinking of building a new comp in approx. six months cause summer always has good deals (plus an insufficient money supply). was wondering what DDR really was. I was gonna go with CAS2 PC133 256Mb. Seeing how there aren't many mobo for DDR i will stick to CAS2. Thanks for the info.