DDR266? DDR333? DDR400?

[hulkMAD]

does DDR266 = PC2700 DDR RAM or something? why do they have 2 different labels? what equals what? what do they mean? someone please explain.

[John Prophet]

its all about the speed they can handle. and one listing is listing the speed, one is listing the calculated bandwidth

I have seen the calculation for the bandwidth but forget what it is.

but

DDR 266 = PC2100
333=PC2700
400=PC3200

here is the formula for ddr

bandwidthDDR SDRAM = d * f * w

= (2 transfers / tick) * (133 * 106 ticks / sec) * (8 bytes / transfer)

= 2,128 * 106 bytes / sec


from http://www.vanshardware.com/articles..._P4X266_BW.htm


JP

[Steve R Jones]

What is the difference between PC2100 (DDR266), PC2700 (DDR333), and PC3200 (DDR400).

PC2100 DDR (DDR 266) is designed for use in systems and motherboards which require a 133MHz front-side bus. While the system or motherboard may operate a 133MHz front-side bus, its effective front-side bus speed is 266MHz in DDR operation. To get the effective front-side bus speed of a DDR system, double the operating frequency -- which in this case is 133 MHz -- to get the 266MHz.

PC2700 DDR (DDR333) is designed for use in systems and motherboards which require a 166MHz front-side bus, with an effective front-side bus speed of 333MHz.

PC3200 DDR (DDR400) is designed for use in systems and motherboards which require a 200MHz front-side bus, with an effective front-side bus speed of 400MHz.

[John Prophet]

I also ran across this

DDR-SDRAM @ 100MHz
(100 MHz Operating Speed) x (2x Rising & Falling) x (64-bit Bus) / (8 bits per byte) = 1600 MB/s available bandwidth.

DDR-SDRAM @ 133MHz
(133.33 MHz Operating Speed) x (2x Rising & Falling) x (64-bit Bus) / (8 bits per byte) = 2133 MB/s available bandwidth.

DDR-SDRAM @ 166MHz
(166.66 MHz Operating Speed) x (2x Rising & Falling) x (64-bit Bus) / (8 bits per byte) = 2667 MB/s available bandwidth.


or if you just simplify it, it is 266x8=2128 333x8=2664 etc

so they sort of round em off

PC1600, 2100, 2700

[HeadBand]

if you are looking into buying some it is good to get faster because it will run slower but if you wanto to overclock or upgrade it will get faster also if you mix types it will run at the speed of the slower one if you have a p4/celeron get atleast 1/2 of your fsb if you have an amd system get the same as your fsb or better

[hulkMAD]

thanks. i got it all down now. one more question. does this:

FSB: 333/266/200MHz
RAM: 3x DIMM for up to 3GB Non-ECC DDR400/333/266/200(DDR400 Max 2 banks,DDR333 4 banks)

make any sense? if FSB is only 333mhz, and the RAM slots can support DDR400, then theres no point in buying DDR400 right? why would a mobo have specifications like this? is FSB measured in DDR (X2)? or can u have, for example, a 333mhz fsb mobo that takes DDR666 ram?

[Xtreeme]

Look at ONE type once.
Pc 2700. Its also called ddr333 as you noticed. Why. K.
Pc2700 is 2.7gig top theoretical bandwidth.
DDR333 is refrence to the mhz the mem runs at. 333mhz. So 333mhz DDR mem is 2.7 gig bandwidth possible. Both names are correct.

"is FSB measured in DDR (X2)? or can u have, for example, a 333mhz fsb mobo that takes DDR666 ram?"

Oy. You dig right in eh? Heh. Yes there are double and quad pumped fsb's. Not measured in ddr like you said as ddr means Double data rate. But double pumped fsb. Or quad. DDR 333 IS for 333mhz cpu in 1:1 ratio.

[John Prophet]

why would you have ddr400 slots when you only have 333fsb??

A good question......the reason is that nowadays the ram often runs at independent speeds from the cpu.....so the ram there can be ran at 400 while the cpu is at 333....just like the older stuff where for instance you can run pc133 memory while running a celeron at 100mhz fsb etc.

[hulkMAD]

ok. thanks. i think i got it now. computers r too technical...