Computer Memory (RAM)

“Are you a technician?”, “Yes”. “Yes! You said yes, then more memory please my computer is slow, put more memory.”…

Computer memory is a physical device (hardware) that stores data and programs (instructions) on temporary or permanent basis and can be read or written or erased or both. Random Access Memory (RAM) commonly referred main / primary memory is a temporary storage device which stores data and instructions that the CPU requires currently as it process. It is also termed volatile because it requires constant supply of power to retain data (memory).

Memory upgrade has great impact on computer performance up to a point. It’s technically advised to take note that:

• motherboards have memory limits
• Operating systems have memory limits
•  CPUs have memory limits.

 So it’s not a ‘…more memory please…’ thing. The listing below is a quick academic summary on RAM, if you note flaws post it for a revision, enjoy.

Types of Memory (RAM)

Dynamic RAM (DRAM)

Special type of memory that uses microscopic capacitors and transistors to store zeros and ones. A single chip can hold millions of these capacitors and transistors in combination thus holding millions of bits. It’s dynamic since the chip needs constant update signal (refresh cycle) in order to retain information, otherwise it will fade off. DRAM is categorized as Asynchronous or Synchronous.

Asynchronous DRAM

Asynchronous because it doesn’t depend on the CPUs external clock, this leads to some increased access time while processor experiences wait times (delay). During wait times the CPU does nothing. They include:

Fast Page Mode (FPM DRAM) - a lower performance and slow memory with better access time than conventional DRAM but maxes out 50 MHz processor speed (outdated)

Click the memory type chart to enlarge

Extended Data Out DRAM (EDO DRAM) – like FPM maxes 50 MHz of processor but slightly faster, has some cache built into its chip. (outdated) 

Synchronous DRAM (SDRAM)

The DRAM whose speed is directly dependant (tied to) on clock speed of system, it’s synchronized with the system bus. Scales speeds above 133 MHz. Designed to write and read from the memory 1 clock cycle per access with a zero wait state (delay). SDRAM is 3.3v and 168 pin module fitting into a DIMM slot.

Double Data Rate SDRAM (DDR SDRAM)

Transfers data twice per clock cycle at the rising and falling edge of the clock, hence double rate (double of conventional SDRAM). Operates at 266 MHz speed, 2.5v with 184 pin DIMM module, is not compatible with SDRAM.

DDR2

Unlike DDR it was designed to provide great bandwidth with reduced power consumption, 333 MHz speed, 1.8v and 240 pin module.

DDR3

A better generation of DDR with Memory with speed of 1000 MHz. Data Transfers/Sec.: 2,000,000,000. Module Name: PC3-16000. Has better voltage consumption.

Direct Rambus DRAM (DRDRAM)

Designed by Rambus Company, uses burst mastering with speeds of 800 MHz and higher, used on a dual channel 32 bit motherboard. Because of the speed it generates a lot of heat, uses RIMM modules.

Synchronous Link DRAM (SLDRAM)

Competitor of DRDRAM speeds up to 400 MHz

Static RAM (SRAM)

Unlike DRAM this is a fast and expensive memory.  It uses electrical pulse to flip its logic state from 1 to 0 or flop from 0 to 1; this state will stay its position till another pulse is received thus static. Because of that it doesn’t require refresh cycle. It includes:

Async SRAM – used for L2 cache and was independent of the system clock, introducing wait states

Synch SRAM – synchronized with the system clock, has good speed but expensive.

Pipeline Burst SRAM – sends larger packets of data to the memory at once, operates at bus speeds above 66 MHz.

Written by Michael Akunga

Courtesy of pcguide.com, pctechguide.com, hexus.net and computermemoryupgrade.net