Memory chips also known as Random Access Memory (RAM) are broken down in various configurations.

Other Memory related pages

* Memory Hardware - prices
* Installing DIMM memory -

One breakdown is the type of memory such as Static or Dynamic. The static type are used for cache and are much faster and expensive than the dynamic type. Dynamic are the most common type used in PCs and are slower and less expensive than the static type.

Another breakdown is the usage of parity. Memory modules can be either Parity or Non-Parity. The Parity type uses an extra bit to store the "parity" information and costs more than the non-parity RAM. Parity and non-Parity memory chips should not be mixed.

The speed of the memory is also critical and is measured in nanoseconds which typically ranges between 15ns and 80ns. The smaller numbers are achieved using static RAM and the higher (slower) numbers are associated with the dynamic RAM.

Physically the chips come is various configurations, most commonly the 3-chip and 8 or 9-chips styles. These styles should not be mixed due to slight timing differences in the operation.

The contacts can be of either Tin or some other inexpensive alloy or gold plated. The gold plated are more expensive but have better longevity and are more resistant to microscopic corrosion of the contacts. Most computers come with the Tin type memory contacts.

RAM evolution : DRAM, SIMM, Fast Paged Mode memory to EDO, to PC66 SDRAM to PC100 SDRAM

SIMM - Single In-Line Memory Modules -

The older style SIMM memory comes in a 30-pin package

Simm30a.gif (9024 bytes)

* Speed 60nanoseconds typical
* 30-pin or 72-pin
* Parity (36 bits ), non-parity ( 32 bits)
* Standard or EDO (Extended Data Out)



DIMM (Dual Inline Memory Module) -

SODIMM -

EDO types

* EDO (Extended Data Out) - This type of memory is a variation on the SIMM chips and uses a two-stage pipeline that allows the motherboard to start the next memory cycle faster. Typical speed increases are in the 5-20% range. A much larger factor affecting speed is the absence of a secondary cache more so than having EDO memory installed. The Triton chipset systems should use EDO RAM

* EDO ECC DRAM is a variation of the EDO style.

* BEDO - Burst EDO another EDO variation

SDRAM ( Synchronous DRAM ) -

Replaced EDO memory and it is faster than EDO. Works well with Pentium MMX systems.

SIPP (Single In-line Pin Package Module)

This is a very old style that looked like a simm but had wire style pins instead of edge connectors and it is not used today.

RDRAM ( Rambus Dynamic Random Access Memory ) -

SLDRAM ( Synchronous Link DRAM )

Memory and Windows 95

Windows 95 needs plenty of memory to operate correctly. At a minimum 16mb is needed but 32mb is even better. Adding memory to a computer helps windows95 by allowing more programs to stay in memory without having to swap them to the hard drive. When there is insufficient memory and more than one program is loaded, the computer will swap to the hard drive as much of the first program as possible to make room for the second or third program you are trying to run. Consequently, the computer runs much slower and you see the hard drive running quite a lot.

In Additions, graphic programs that load large images will show a large improvement in speed with more RAM as will large spreadsheets.

Almost all Pentium computer systems at this time use non parity memory.

Remember to always add modules in pairs to avoid timing problems.

EDO and standard SIMMS could be mixed on many computers as long as the speeds are the same but again this is not recommended.