Set 5 — RAM and Memory

DDR

184-pin, roughly double the speed of SDRAM

DDR2

240-pin, higher latency but faster bus, max 4GB per module

DDR3

240-pin (keyed), lower voltage/higher speed, max 8GB per module

DDR4

288-pin, max 32GB per module

DDR5

288-pin, max 128GB per module

SODIMM

Smaller RAM module for laptops/compact systems (DDR3/4/5)

DRAM

Oldest RAM type, needs constant refreshing

SRAM

No refresh needed, but expensive - used for CPU cache

SDRAM

First RAM synced to the motherboard bus speed (PC66/PC100/PC133)

Buying RAM rule

Match speeds - mismatched sticks run at the SLOWER speed

Single channel

One memory controller pathway - baseline speed

Dual channel

Two pathways used together - roughly doubles bandwidth

Triple/Quad channel

Three/four pathways - further increases bandwidth (HEDT/server boards)

ECC RAM

Error Correcting Code - detects/fixes memory errors, used in servers

Non-ECC RAM

Standard consumer RAM, no built-in error correction

Virtual memory

Uses space on the storage drive (page file) as overflow "RAM"

Page file / swap file

The file on disk that virtual memory writes to

CAS latency

Delay (in clock cycles) between a RAM request and the response - lower is faster

Throughput (RAM)

Calculated from bus speed x data bus width