DDRAM, SDRAM, ECC and non ECC Modules a few questions.

[Kev Nurse]

Hi guys,
I recently had a discussion with my local pc dealer about RAM module
characteristics. In particular we discussed how to identify DDRAM from
SDRAM. One of us believes that SDRAM modules always have 2 notches and
that DDRAM always has 1 notch and that there is no such thing as a DDR
SDRAM module. An interesting 1Gb 184 pin module, with only one notch,
was then produced for examination and it had "DDR SDRAM" written on it.
It was fitted onto a mobo that only accepts non-ECC DDR but the pc
rejected it on boot up. I have a few questions:

1. Is "DDR SDRAM" a misprint?

2. If not, does this mean that DDR SDRAM is always ECC?

3. The examined module has 9 chips per side. Is this a distinguishing
characteristic of an ECC module? I have read that an extra chip is
fitted on each side to cater for the error checking.

Thanks for any answers that you might have.

Regards
Kev Nurse

 

[Shoo]

http://home.pacbell.net/dbk4297/memory_what_kind.html

 

[Mike T.]

Hi guys,
I recently had a discussion with my local pc dealer about RAM module
characteristics. In particular we discussed how to identify DDRAM from
SDRAM. One of us believes that SDRAM modules always have 2 notches and
that DDRAM always has 1 notch and that there is no such thing as a DDR
SDRAM module. An interesting 1Gb 184 pin module, with only one notch,
was then produced for examination and it had "DDR SDRAM" written on it.
It was fitted onto a mobo that only accepts non-ECC DDR but the pc
rejected it on boot up. I have a few questions:

1. Is "DDR SDRAM" a misprint?

Not at all. It's all SDRAM. DDR means that it's SDRAM running at a double
data rate. Or, that it performs two functions per clock cycle.

2. If not, does this mean that DDR SDRAM is always ECC?

ECC is entirely different term. If it's ECC, it should say so.

3. The examined module has 9 chips per side. Is this a distinguishing
characteristic of an ECC module? I have read that an extra chip is
fitted on each side to cater for the error checking.

That totally depends on the chipset. There is no answer. ECC has an extra
bit, but that doesn't necessarily mean an extra chip. -Dave

 

[DaveW]

Therre is no such thing as "DDRAM." There is standard SDRAM, and a more
advanced version called DDR SDRAM. They are both SDRAM type RAM, but the
second one runs at double the speed of the FSB. DDR RAM has more pins and
requires a different socket and a different voltage than standard SDRAM.
DDR RAM comes in both ECC and non-ECC.