Physical Memory Review

1. Physical Memory Review • Temporarily holds data and instructions as CPU processes them • Two categories • ROM • Retains its data when PC is turned off • Stores data on chips socketed or soldered to circuit boards • RAM • Loses its data when PC is turned off • Housed on SIMMs, DIMMs, or RIMMs

2. ROM on the Motherboard • Consists of memory chips that contain programs (ROM BIOS) that are acid-etched into the chips and cannot be changed • EPROM (erasable programmable ROM) and EEPROM (electrically erasable programmable ROM) chips can be reprogrammed

3. ROM on the Motherboard

4. RAM on the Motherboard • Serves as main memory • Provides a memory cache • Two categories • Dynamic RAM (DRAM) • Needs to be refreshed by the memory controller • Usually stored on DIMMs, less commonly on RIMMs • Static RAM (SRAM)

5. DRAM Storage

6. SRAM Storage

7. Static RAM Technologies • Provide faster access than DRAM because data does not need to be constantly rewritten to SRAM • SRAM chips are made of transistors that can hold a charge • DRAM chips are made of capacitors that must be recharged • Due to expense of SRAM chips, most computers have a little SRAM and a lot of DRAM

8. Dynamic RAM Technologies • Always stored in SIMMs, DIMMs, or RIMM modules • Major differences among modules: • Width of the data path that each accommodates • The way data moves from system bus to module • Goal is to increase overall throughput while retaining accuracy

9. Examples of Memory Modules

10. DIMM Technologies

11. Installing Memory • Protect chips against static electricity • Use a ground bracelet • Turn off power and remove cover to case • Handle memory modules with care