Memory Types

Volatile

loses its contents when power isn’t present

Nonvolatile memory

doesn’t lose its contents when power is removed

RAM

Volatile. The working memory for your computer

CMOS

Volatile. The storage location for BIOS configuration data, requires a battery to retain its information

ROM

Nonvolatile. Used to store the BIOS and other programs and data that must be preserved when the computer is unplugged, must be written at the factory

PROM

Nonvolatile. Must be programmed at the factory and can be programmed only once using a burner

EPROM

Nonvolatile. You can erase the contents chip by exposing its glass window to ultraviolet light. You can program the chip by using a burner.

EEPROM

Nonvolatile. You can erase and program the contents chip by using a burner or special circuitry within your computer

Flash

Nonvolatile. Chips that don’t lose their memory when power is removed and can be burned using burners or circuitry within your computer. Memory is written block by block.

complementary metal-oxide semiconductor

CMOS

Programmable read-only memory

PROM

Erasable programmable read-only memory

EPROM

Electronically (EEPROM)

Electronically erasable programmable read-only memory

Similar to EEPROM

Flash

DRAM (dynamic Ram)

must be refreshed hundred of times per second

SRAM (static Ram)

does not need to be refreshed, the memory holds its contents until power is removed.

Asynchronous DRAM

isn’t synchronized to the system clock.

Synchronous DRAM (SDRAM)

is tied to the system clock (faster)

Bandwidth

is the amount of data that can be transferred to or from memory per second

latency

the amount of time between when an address (of the data being requested) arrives on the bus and when the memory is ready to return that data

hertz

a cycle per second

megahertz

is a million cycles per second

Access time

is the overall amount of time between when a request is made and when the data is available on the bus

nanosecond

is a billionth of a second