What is the difference between double sided ram and single sided ram?

[Jmartin]

I was just reading up on my motherboards dimm slot configuration and i read where if i put single sided ram in all 4 slots it will run at DDR400..if i put double sided ram in all 4 slots it will run at DDR 333...whats the difference in the ram? (and please dont say one has chips on the other side). What are the benifits from having single sided ram from having double sided ram?

 

[her209]

One has chips on the other side.

 

[Peter]

With fewer chips on the DIMM, the signal integrity on the common bus will be less affected, and thus, a higher speed will be achievable.

 

[otispunkmeyer]

Originally posted by: Peter
With fewer chips on the DIMM, the signal integrity on the common bus will be less affected, and thus, a higher speed will be achievable.

which is why alot of very serious overclockers can be found using just 256mb of ram, as most of it is single sided.

 

[syadnom]

though not identical, use the same reasoning as why a processor can run at 2Ghz but not 4Ghz. signal integrity falls. single sided memory is less complex in signalling having 1/2 as much data running down the pipe, so it is more stable.

 

[Peter]

No you don't have "half as much data running down the pipe". The signal integrity is better with fewer chips because every piece of silicon and every length of PCB trace introduces parasitic capacitance onto the common bus, which washes out the signal transitions from sharp edges to slower slopes, thus limiting the maximum operating frequency of that bus.

 

[harrkev]

The best way to think of a double-sided RAM as being two single-sided RAMs glued together back-to-back.

The problem is that there are various wires that go to these RAMS. When you double the number of chips attached, you double the capacative loading. In short, it now takes more electrons traveling down the wire in order to send the signal. This means that it now takes just a little bit longer, and you have to slow down as a result.

But having said that, even slow RAM is a LOT faster than paging to the hard drive. So ripping out half of your RAM is more likely to hurt than to help.

 

[zailex]

i have a ocz rev3 series ddr400 2-3-3-6 memory stick which has heat spread stuff on it so i can't see if its single sided or double sided. Does anyone know what it is?

 

[EightySix Four]

how big it is what will tell us.... Generally 512mb and up is double... AFAIK at least.

 

[zailex]

its 512... so its most likely double sided?

 

[Peter]

Not necessarily. Since the production focus is currently shifted over to 512-megabit SDRAM, single-sided 512-megabyte DIMMs are becoming commonplace now.

 

[ribbon13]

http://www.monarchcomputer.com/Merchant2/graphics/00000001/140827.jpg

That's a lot of chips on one DIMM

 

[Peter]

That's a "registered" DIMM. Still only two ranks - each rank made from 16 pcs of "x4" geometry chips, 36 chips total for two ranks of 72-bit width for ECC purposes. The very reason why there are those "register" chiplets (plus a clock PLL) on those DIMMs is to isolate the capacitive load of those many RAM chips from the common bus. Spot on the topic, this

On an "unbuffered" DIMM, you're done with 18 chips max, and thus, with the highest available chip density a given, half the capacity of the biggest possible "registered" DIMM.

Normally, those high capacity reg-DIMMs are made with "stacked" chips (two on top of each other), making the DIMM thicker not taller.

 

[ribbon13]

Speaking of registered, I wonder how the opeterons will overclock on the Abit WN-2S+ with that nifty unbuffered ram support. People are calling using unbuffered on an Opteron 'Black Magic'