[adeel420] MEMORY
- From: "Sajid Iqbal" <sajid_cyberspace@xxxxxxxxxx>
- To: <"Undisclosed-Recipient:;"@smtp-1.hotpop.com>
- Date: Mon, 25 Nov 2002 22:31:10 +0500
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MEMORY PACKAGING
The packaging is simply the entire makeup of a unit of memory, in most
cases, the SIMM. Since the memory chips themselves are way too small, they
must be combined and put on a medium that can be worked with and added to a
system. So, designers took the memory chips, placed them on a small
fiberglass card, and created the SIMM.
The memory chips themselves are called DIPs, or Dual Inline Packages. These
are the black chips you see when looking at a SIMM. In the old days, these
chips were either soldered onto the motherboard or placed in special
sockets. Unfortunately, this meant that when a memory chip went bad, you had
to replace the whole motherboard. With socketed chips, chip creep became the
problem. This was the term for chips being lodged out of the socket due to
thermal expansion. You had to periodically remove the case cover and push
the chips back in with a thumb.
Finally, engineers put the chips on SIMMs, or Single Inline Memory Modules,
or DIMMs, Double InlineMemory Modules. These cards are placed in a socket on
the motherboard, like a card in a slot, then latched in. This design
eliminated problems of the past, and made upgrading memory a breeze.
SIMMS
The SIMM is the most popular memory module, even with the rise of DIMM use.
They come in two sizes, 30-pin and 72-pin. The 30 pin SIMMs usually came
with small amounts of memory (smaller than 8MB). They are not used much
anymore, being mainly used in earlier 486's and older machines. The 72-pin
SIMMs are much more popular now, and are used on many modern motherboards.
SIMM Diagram
SIMMs come in both single sided and double sided designs. This refers to
whether the SIMM has DIP chips on one side of the SIMM or both. Usually, 1,
4, and 16MB SIMMs are single sided. Other sizes are double sided. Some
double sided SIMMs are actually two single sided SIMMS back to back, wired
together within the fiberglass module. These designs operate a little
different electrically, explaining why some boards only use SIMMs of certain
sizes.
DIMMS
The DIMM is a newer memory module. It has 168 pins and provides a 64-bit
memory pathway. It isn't used on older motherboards, being confined to fifth
and sixth generation machines. The popular SDRAM comes on DIMMs.
An architectural difference is the pin designs. SIMMs have either 30 or 72
pins, and these pins are for both sides of the module. A DIMM actually has
83 pins on each side. These pins are more like little pads of metal. This
design allows more performance while maintaining a small package size. It
also makes it even more imperative that the connection remain intact with
all the "pads."
DIMMs come in either 3.3 volt or 5 volt designs, and unbuffered or buffered.
This leads to 4 choices. The most common is the 3.3 volt unbuffered,
although you need to consult your motherboard's documentation to determine
the type you really should have.
CONNECTORS
Memory modules come with both gold and tin connectors. Older motherboards
usually use the gold connector, while the newer systems use tin ones. You
can tell by simply looking at the SIMM or DIMM and checking out the color of
the connectors. Also look at the SIMM sockets.
Make sure you use the type of connector your board uses. If you mix-match
them, over time a chemical reaction will take place between the connectors.
The product of that reaction can cause unreliability and errors.
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