SDRAM or DDRAM in linux

[Tim]

On Mon, 2006-08-28 at 23:10 +0530, Niklaus wrote:
> 1) How do i find out when the machine is online , if it is SDRAM or
> DDRAM. I tried dmidecode utility but i was not sure about the type.
> Can someone help me out by pasting the output for both DDR and SDRAM
> in dmidecode or similar.

Does dmidecode tell you what model motherboard you have?  If so, you can
research what it needs, that way.

> 2) Can both SDRAM and DDRAM be present at a time in the same
> motherboard. I mean can i have 256MB of SDRAM chip and a 256 MB of
> DDRAM on the same motherboard.
> 
> If yes what are the conditions.
> 
> 
> 3) Is a motherboard designed for only one type of RAM , like if we
> remove all the SDRAMs can we put DDR in it or it is either designed
> for DDR or SDRAM.

What most people refer to as SDRAM and DDR are physically different.
Your board would use one or the other, unless it had multiple slots.

However, what people call SDRAM and DDR are often rather poor
descriptions, which pedantically are the same thing (they've both
"SDRAM", but the second being "double-data-rate" SDRAM).  And DDR has
variations, too.  

My motherboard uses what's generally known as DDR 400 RAM, and it goes
into a DIMM socket.  But that's a 184-pin DIMM socket.  Generally, what
people refer to as SDRAM is another thing, again.

The dmidecode utility reports this for my motherboard:

        Supported Memory Types:
                DIMM
                SDRAM

And if I asked for that at a computer shop, I'd get the wrong memory.
But, on the other hand, if I ask for what's described in the manual (see
below), I'd get the right thing:

  2 x 184-pin DDR DIMM sockets for up to 2GB memory
  Supports PC3200/2700/2100 unbuffered non-ECC DDR DIMMs.

Another board says:

  Supports PC100 SDRAM 16MB~512MB total, 256 MB maximum per 168 pin module

And that's the type that most people call "DIMM" RAM.

DIMM just means dual in-line memory module.  You need to know the number
of pins it has.

SDRAM means synchronous dynamic random access memories, which is the
techology inside the RAM.  It's used on a variety of different types of
RAM.

DDR SDRAM means double-data-rate SDRAM.

There are plenty of other types of RAM, too.  Different types are more
prevalent in server boards rather than general-purpose PC motherboards.
Find out what motherboard you have, that's really the best thing to do.
You might even find out, that way, which RAM is best suited, or best
avoided.  There are known incompatibility issues with some, and you need
to know the right type, as well as how much RAM can be installed.

-- 
(Currently testing FC5, but still running FC4, if that's important.)

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