Is PC2700 memory backwards compatible to PC100

[NicColt]

In other words can I put a stick of PC2700 DDR Memory in a KT133 board that only supports PC100 SDRAM memory ?

 

[Elminster]

heh they aren't even close to being pin compatible man.

 

[Peter]

No. Best you can do is PC133 SDRAM. This is the same technology, and doesn't mind being run slower than intended.

 

[Actaeon]

Originally posted by: Peter
No. Best you can do is PC133 SDRAM. This is the same technology, and doesn't mind being run slower than intended.

Yep.

 

[Passions]

PC2700=DDR.
PC100=SDRAM.

Not compatible at all.

 

[Kazuo]

People need to stop spreading this fallacy. DDR *is* SDRAM. It's Double Data Rate Synchronous Dynamic Random Access Memory, or DDR SDRAM. Just because it's double the FSB speed doesn't mean all of a sudden the synchronization was lost.
What most people refer to as SDRAM is SDR SDRAM, but single data rate is implied when it's not said.
So stop it!

 

[Peter]

... but when you're nitpicking, then at least get it right. The FSB moniker isn't used here, this is a term used for the CPU side of things, not the RAM bus. And then, DDR SDRAM does _not_ use a doubled clock frequency, but instead issues a data word every half clock cycle.

Yet still, incompatible it is ... because a chipset that expects SDR SDRAM would miss every other transmission from/to DDR RAM.

regards, Peter

 

[WarSong]

SDRAM uses a 168-pin DIMM while DDR uses a 184-pin DIMM. They aren't even physically compatible AFAIK.

 

[dmcowen674]

The only memory trick or recycle you can do is put a doublesided chip in an older board that only recognizes single sided memory. Of course you lose half the capacity of the size of the memory. I'll give an example: Put a 64 Meg double sided DIMM in an old K6 MB that had single sided 16 meg chips in it. It only recognizes 32 Meg added.

 

[Peter]

That's not because of a lack of "sides support". It's because 1st generation SDRAM supporting chipsets didn't handle more than 16 MBytes per DIMM side - and that's why you ended up with a maximum of 32 MBytes per double sided DIMM, no matter how big it really is.

regards, Peter

 

[Kazuo]

OK, you're right, it doesn't have to run synchronously with the front side bus. My bad. (It was just originally meant to.)
And you're right again, I shouldn't have said it's double the speed, it transfers data double as frequently as SDR, but it still uses the same clock signal. It just transfers on both clock edges.
Anyway, my point is that there's still no excuse for people saying DDR isn't SDRAM. It is.

 

[CrazySaint]

Originally posted by: Kazuo
OK, you're right, it doesn't have to run synchronously with the front side bus. My bad. (It was just originally meant to.)
And you're right again, I shouldn't have said it's double the speed, it transfers data double as frequently as SDR, but it still uses the same clock signal. It just transfers on both clock edges.
Anyway, my point is that there's still no excuse for people saying DDR isn't SDRAM. It is.

AFAIK, nobody said that DDR isn't SDRAM (though that's certainly an easy mistake for some to make), what they said was that the two are completely incompatible (which they are).