6. Main Memory

• Random Access Memory

  • Storage for data and instructions for executing programs (aka processes)

  • Common today to see 256 MB to 2 GB or more

  • Entire programs can be hidden, run as RAM-resident, and will disappear when the computer is powered down

• Cache memory

  • Very fast (expensive) memory to store most recently used data and instructions

  • Level 1 cache is internal to the CPU;

  • Level 2 cache is external;

  • Level 3 cache is on another chip