30 – Pin SIMM

Single In-Line Memory Module

9-bit 3O Pin SIMMs
This memory is used in PCs mostly 286, 386 and early 486 based machines).

They are usually installed in sets of four i.e. 4pcs of 1MB SIMMs giving 4MB or 4pcs of 4MB SIMMs giving 16MB.

• 72-Pin SIMM Memory Modules                                           72 Pin SIMMs is already the most popular variety and are used in newer 486 and Pentium PCs.                                            Available in 4MB, 8MB, 16MB, 32MB and for high end machines 64MB capacities.

• 32-bit 72- pin SIMMs without Parity FPM (Fast-Page-Mode)

• 32-bit 72-pin SIMMs without Parity EDO
  This type of memory is fast becoming the most popular in the latest PCs.

• 36-bit 72-pin SIMMs with Parity FPM
  FPM (Fast Page Mode) with Parity.

• Parity chips are used to check the integrity of the memory

• Static random access memory uses multiple transistors, typically four to six, for each memory cell but doesn’t have a capacitor in each cell. It is used primarily for cache.

• Dynamic random access memory has memory cells with a paired transistor and capacitor requiring constant refreshing.

DIMMs (Dual In-Line Memory Module) is used in the latest Pentium Desktops, Servers and Portables 

There are three physical sizes of DIMMs:

• The Long DIMM (133mm long) has 168 pins and two notches. These tend to be installed in desktops and servers as singles but some machines require pairs.

• The SODIMM has either 72 pins (60mm, no notch) or 144 pins (68mm single notch).
  SODIMMS are used exclusively in portables (Laptop).

• DIMMs can be 3.3 Volt or 5.0 Volt: The voltage of the DIMM must match the voltage of the machine.

• FPM DRAM was the original form of DRAM. It waits through the entire process of locating a bit of data by column and row and then reading the bit before it starts on the next bit.

• EDO DRAM does not wait for all of the processing of the first bit before continuing to the next one. As soon as the address of the first bit is located, EDO DRAM begins looking for the next bit. It is about five percent faster than FPM.

168-Pin SDRAM Memory Modules

Synchronous dynamic random access memory

• It takes advantage of the burst mode concept to greatly improve performance. It does this by staying on the row containing the requested bit and moving rapidly through the columns, reading each bit as it goes. The idea is that most of the time the data needed by the CPU will be in sequence.

• SDRAM is about five percent faster than EDO RAM.

• Maximum transfer rate to L2 cache is approximately 528 MBps

184-Pin DDR Memory Modules

• Double data rate synchronous dynamic RAM is just like SDRAM except that is has higher bandwidth, meaning greater speed.

• Maximum transfer rate to L2 cache is approximately 1,064 MBps (for DDR SDRAM 133MHZ).

184-Pin Rambus / RDRAM MemoryModules

Rambus dynamic random access memory

• It is a radical departure from the previous DRAM architecture. Designed by Rambus, RDRAM uses a Rambus in-line memory module (RIMM), which is similar in size and pin configuration to a standard DIMM. What makes RDRAM so different is its use of a special high-speed data bus called the Rambus channel.

• RDRAM memory chips work in parallel to achieve a data rate of 800 MHz, or 1,600 MBps.

72-Pin / 144-Pin SODIMM Memory Modules

144-Pin MicroDIMM Memory Modules

200-Pin SODIMM Memory Modules

Portable computers require smaller sticks of RAM because of their smaller size. Two types are small outline DIMM (S0DIMM) and MicroDIMM.