single-sided SIMMs?

[SLPFirehawk]

This is my first post on this forum. I've been snooping around and it looks like there is a lot of knowledge floating around here.

My question pertains to single-sided SIMMs. First, what is the difference between single-sided and double sided SIMMs? Where can I get some 64MB single-sided SIMMs?

Any insight would be greatly appreciated!
Joe

 

[ruckb]

Hi,

before trying to answer your question one thing I would like to know
for sure:

Are you talking about SIMMs ?

So you are talking about the older 72pin memory ?
Not about 168pin SDRAM DIMM!

ruckb

 

[SLPFirehawk]

Yes...I am talking about the older 72 pin SIMMs.

Thanks

 

[ElFenix]

i think i have some double sided simms. it may be just a way to cram more memory chips on a wafer. with dimms if its double sided its a full bank, with single sided its a half bank, i think. but banks are always in pairs with simms...

 

[ElFenix]

soy muy estupado

 

[loveturtle]

I got some of both in my dads old pc
I think that the single side are just less space,prehaps die shrinks
it doesnt seem to make a difference in performance,I had both
I could be wrong but I would think one is manufactured on a smaller die thus more memory in smaller package and no need for double sided pc board(this would make sense since it would be cheaper to make a single sided one I think)

 

[cvlegion]

well, may be I am missing something but a simm can only be single-sided and a dimm can only be double-sided by definition. Single-Inline Memory Module and Dual-Inline Memory Module. Now how many it pins it has is another issue.

 

[Topochicho]

first of all... its Single-Inline Memory Module not Single-sided-Inli...

The difference between single sided and dual is simply transistor density. Some Manufacturers found it cheaper to use many low density chips on a simm and others went with highdensity. Just like using four 8MB simms instead of two 16MB in a computer. Amounts to the same thing. My Kingmax 128MB PC150 has just a few really tiny and flat chips on one side. My older no-name 32MB PC66 has twice as many chips that are twice the size.

Don't assume less chips mean high quality. High density chips can be made to low standards. So be more conserned with the maker of the sim and its performance.

 

[loveturtle]

prehaps my memory is going but I am sure that that pc has chips on both sides of that fpm dram pc board
and DIMMs can have chips on just one side,mushkin seels a lot of them

 

[thorin]

Heh you guys are young and funny. You equate SIMMS automatically with 72pin RAM Modules.

I hate to break it to you but the acronym SIMMs (Single InLine Memory Modules) refers to both 30pin and 72pin RAM Modules.

And before that were DIPs (Dual Inline Packages) single memory chips you plug straight in to the MotherBoard.

"The difference between single sided and dual is simply transistor density. "

Exactly. Some manufacturers decided to use 8 or 9 low density chips and some decided to use 3 to 5 high density chips.

Thorin

 

[SLPFirehawk]

Where can I buy 64MB single-sided SIMMs? And how can one tell that it is single-sided and not double-sided?

 

[ruckb]

Hi,

I missed some posts, because I was offline some time!

First there is one very important questione missing:
I would assume you need EDO/FPM, right ?
Just because I have never seen SDRAM on a 72pin SIMM.

and thorin:
you are right, SIMM was both 30 pin and 72 pin, but SLPFirehawk has already answered, that he needs 72pin SIMMs.

But I have one very important question to you (at least important for me ;-) ):
"to use 3 to 5 high density chips"
==> as the older systems had a databuswith of 64bit, but the SIMMs where just 32 bit you had to use 2 SIMMs at the same time (at least, what I can recover from my badly refreshed memory). So one SIMM had a datawith of 32bit. You could
archive this by using 8 x4 devices (or 9 for an ECC DIMM ?!?)
But how was this done "3 to 5" high density chips.
2 x16 devices or 4 x8 organized devices, but what device was used for ECC ? Still a x4 device ?
Do you have informations about these kind of SIMMs ?

And now I try to answer (partly) the questione of SLPFirehawk:
What I write now is just extrapolated from my knowledge about DIMMs, therefore
some things could be wrong:
It should be mentioned on the web side of the manufacterer whether it is single or doublesided.
If you can take a look at the DIMM you can check the overall number of the DQ's. You have to check the print on a single memory device, and check the manufacterers homepage about the number of DQs per device. If the overall number of DQs is 32, then it is single sided, if 64, then it would be doublesided.
The other thing is that you are looking for a 64MB module. This means for a DIMM (64 bit databus), that you have 8 x8 64M devices on it. So it should be possible, that a SIMM is built of 8 x4 64M devices. So I would assume it should be possible to get this "single sided 64M SIMMs", because I know, that there where produced some 64M EDO devices.
I think Apple used longer times EDO. maybe you can find some SIMMs there (but I do not know whether they have the same specs)!



I will check some webpages. If I find something I will let you know!

ruckb

 

[ruckb]

Check out this link:

EOL products from Samsung

ruckb

 

[thorin]

Actually I can't answer to ECC but the difference between 8 and 9 chip SIMMs was parity, 8 chips SIMMs were non-parity and 9 chips SIMMs were parity (8bits=1 byte + 1 parity bit). So when you change to a higher density chip you end up with 4 or 5 chips. (My original post said 3 to 5 but should have been 4 or 5).

Description of Parity checking:
Parity bit = 1 if the data byte contains an even number of 1s
Parity bit = 0 if the data by byte contains an odd number of 1s

Parity can only tell you if there's an error it can not correct it. ECC can detect 1 to 4 bit errors and correct 1 bit errors, for errors large then 1 bit it reports a parity error and refetches the data.

Here's a good blurb I found that may clear things but better then me:

If you see a 72-pin SIMM with a x39 or x40 width specification, you can be reasonably certain that the SIMM is designed exclusively for ECC. However, some high-end PCs and many file servers use pairs of x36 SIMMs for ECC error checking. Two x36 SIMMs supply a total of 72 bits; 64 bits are used for data and 8 bits are used for ECC. This can be confusing because when these same x36 modules are used in other configurations, they are simply parity modules. This reinforces the point that whether or not a system performs parity or ECC error checking depends more on the memory controller than it does on the memory module. The memory module provides the bits, but it is the memory controller that decides how they will be used. Generally, in order to use ECC memory, your computer must include a memory controller designed to take advantage of ECC technology.


Thorin