"Single Stack" vs. "Double Stack"

DannyTheDamager · Apr 15, 2005

Hi Guys,

I've been underrgoing my RAM education as part of the process of my first build and I have a lingering question for you vets...what is up with "single stack" vs. "doublee stack" i.e. the modules with a row of single ships vs the moduels with a row of chips stacked one over teh other? Is this the same as Single Rank vs. Dual Rank? I am told to avoid "double stack" modules because they get really hot.

OK, now, I need to buy 2GB modules of 400mhz PC3200 ram for my setup and I am having a hard time hunting down these modules. The documentation for my MOBO (Tyan K8we) claims I can only use:

Infineon
SM12872RDDR8H2BGIC
(HYB25D512400BC-5)

But I know this is not the case becasue others are using Corsiar and OCZ 2GB modules. I think I could use the Kingstons as well.

Any comments?

DannyTheDamager · Apr 15, 2005

Here's what brought this to my attention...

Some advice:

no matter who you get it from specify that you want "single stack"

Confused?

In other words there are chips on both sides of the module but the profile shows one on one side and one on the other.

Not two stacked on top of each other on both sides.(4 chips per area. So on a single stack there may be space for 9 chips on each side. A double stack will have 18 on each side, but in the same areas as the nine.

1 over 1, not 2 over 2.

If you use the double stack - you will have voltage and heat issues whenever you actuallu populate all the slots.

Never ever use double stack for anything! It's a compromise.

Comments?

fldrice · Apr 15, 2005

I don't know if this is going to help, but I think this is correct...
Taken from Kingston's official site:

STACKING

Many large servers and workstations require higher capacity modules in order to reach system memory capacities of several gigabytes or more. There are two ways to increase the capacity of a module. Manufacturers can stack chips on top of one another, or they can stack boards.

CHIP STACKING
With chip stacking, two chips are stacked together and occupy the space that one chip would normally take up. In some cases, the stacking is done internally at the chip manufacturing plant and can actually appear to be one chip. In other cases the chips are stacked externally. The example below shows two externally stacked chips.

Example of externally stacked chips.
BOARD STACKING
As you might expect, board stacking involves putting two memory module printed circuit boards (PCBs) together. With board stacking, a secondary board mounts onto the primary board, which fits into the memory socket on the system motherboard.

You may also be asking about "rank":
The term "rank" refers to the number of chip select lines on memory module. A module can be physically double-sided (has chips on both sides) but still single rank. Single-sided modules are usually always single-rank.

DannyTheDamager · Apr 16, 2005

Yes, I came across this info from Kingston earlier tonight...I don't think it is what I am talking about though...

Take a look here...

http://www.smartm.com/binary/files/4GBPC3200.pdf

The really big module on the far right in the pic is a "double stack" although this may not be the proper term for it.

fldrice · Apr 16, 2005

Well the module all the way to left looks like chip stacking. I guess instead of stacking two PCBs together, the other two modules look like the PCB has been extended like SODIMMs.

DannyTheDamager · Apr 16, 2005

Thanks for the reply...so in either case, does anyone knwo the performance differences associated with this versus a "single stack" archetecture? Is this bit about the increased heat and voltage correct?

Zulu-1 · Apr 16, 2005

you would think it would probably be slower, because of the higher latancies of having two PCB's instead of one

"Single Stack" vs. "Double Stack"

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