Simm vs. Dimm

[Da_Flea]

what is the difference in these mememory...i knwo the slots are different...but what is better to have more of...? what does each do? what about EDO and SDRAM
???

questions i never ever have goten good answers for,,,,,,please reply...jeff

[Fingers]

DIMMS use connectors that have contacts on both sides of the socket, SIMMS use only one side. The name "Single Inline Memory Module" and "Dual Inline Memory Module" refers to the connectors on the base of the module, not the location of the chips on the module. Both types can have memory chips located on both front and back of the module.

SDRAM is 5-10 times faster than EDO. SIMMS are much older technology than DIMMS and the common 72-pin modules mostly used either Fast Page or EDO ram. DIMMS are newer and use primarily SDRAM chips on a module that uses a 168-pin connector. (The new DDR uses a 184-pin DIMM)

Crucial.com is the best place I know of to expand your basic knowledge about computer memory. Here are two questions from their FAQ (http://support.crucial.com/scripts/crucial.exe/faq) , as well as some other useful links from their site.

What is the difference between a DIMM and a SIMM? (http://support.crucial.com/scripts/crucial.exe/solution?11=001115-0007&130=000974323644&14=&2715=&15=&2716=&57=search&58=&2900=&25=6&3=simm)

What is the difference between EDO and SDRAM? (http://support.crucial.com/scripts/crucial.exe/solution?11=001115-0005&130=000974321133&14=&2715=&15=&2716=&57=search&58=&2900=&25=6&3=edo)

Glossary of memory terms (http://www.crucial.com/library/glossary.asp)

Memory Module Identification (http://www.crucial.com/library/memorymodid.asp)

The S-Files (http://www.crucial.com/library/sfiles1.asp)

If you still don't feel like you've gotten good answers, feel free to say so. http://www.sysopt.com/forum/smile.gif

[DanU]

SIMM = Single In-line Memory Module. "Single In-line" means that there is a single row of contacts (or "pins"). Note that the back side contacts of a SIMM are the same as
the front, resulting in a redundant connection. SIMMS commonly come in 30 pin and 72 pin flavors, although there are others as well. "Memory Module" means that it's a collection of memory chips.
To be completely accurate, 72-pin SIMMS need to be installed in pairs because their data bus is 32 bits wide and the pentium data bus is 64 bits wide. You need to run two 72-pin SIMMS in parallel to "fill" the bus. On a 486, which has a 32 bit data bus, 72-pin SIMMS can be installed singly.

DIMM = dual in-line memory module. This time there are two rows of contacts on the memory module. The front side and the back side contacts are now independent. The most common format is the 168-pin DIMM, which has two rows of 84 contacts. A 168-pin DIMM is already 64 bits wide, so you can install them singly in socket7/P6/K7 systems.

EDO = Extended Data Out. This was a minor improvement over older FPM (fast page mode) memory. Perhaps someone more qualified than I can fully explain the difference between EDO and FPM.
72-pin EDO SIMMS are very common in many older (non-super) socket 7 systems. It's also possible to find 168-pin EDO DIMMS. EDO was eventually superceded by SDRAM in mainstream systems.

SDRAM = Synchronous Dynamic Random Access Memory. This one gets me. Technically EDO and FPM SIMMS are synchronous, too, because they are clocked using the same system clock as the rest of the motherboard. I'd like to see someone explain why it's called SDRAM to ME.
Anyway... SDRAM is supposed to be superior to EDO and FPM DRAMs. It typically comes in 168-pin DIMMs. It also comes in various speed grades like PC66, PC100 and PC133.

[Timbob505]

Simms are found only on older mobos and are slower than most dimms. Yes, simms do have to be installed in pairs (2 X 16MB = 32MB) whereas you only need 1 dimm installed at a time. Dimms come in yummy flavors and speeds up to PC150 I believe. Then there is DDR memory which looks like standard Dimms, but only fits in its own slot. Hope this clears up some stuff for you. Others can and will get more technical if you want. See ya!

Timbob

<edit> DANG!! I am slow!!!!!!!! Oh well, I responded, at least my intentions were good, too bad everyone beat me to it!

[This message has been edited by Timbob505 (edited 06-02-2001).]

[Fingers]

DanU, here's a quote from the aformentioned S-Files (http://www.crucial.com/library/sfiles2.asp) at Crucial:
Both FPM and EDO are said to be asynchronous. In other words, the memory and the system clock are not synchronized. They perform functions independently and have to wait for each other to move data.

... SDRAM is built on the foundation of standard DRAM but uses its feature of synchronous operation to help eliminate wait-times (waiting for a copy center employee to take your order, then waiting around for the job to be completed). When the CPU is ready to access data from the DRAM, it automatically goes to a specified clock point since the processor already knows when operations are going to be completed and data is going to be available. After all is said and done, the processor's ability to retrieve and process data is vastly improved.

[Richard_Cranium72]

The typical speed of 72 pin SIMM's is 60-70 ns

SDRAM ranges,, uhhh, I think from 7.5-8.5 ns

As far as 72 pin memory goes, FPM or Fast Page Mode is slower than EDO memory

hope this heips, somehow http://www.sysopt.com/forum/smile.gif

DrVette

[DanU]

Thanks for the quote AND the link Fingers. Good stuff in there!

[JacobM5727]

if i am correct (wich i doubt), simms have to be installed in pairs

also, i think edo is just a better type of an older memory type i think.. well, maybe. i think simm and dimm is the casing of the ram... you know what, i might just not know what i am talking about so ignore most of this post http://www.sysopt.com/forum/smile.gif