Lenovo PC 300GL Understanding Your Personal Computer 6267, 6277, 6287 - Page 11

Main Memory, CMOS Memory, Flash Memory, These SDRAM modules

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of memory, the computer can store over 1 000 000 characters of information. The computer organizes its memory by assigning an address to each byte as a point of reference. The first address is 0, and the addresses increase sequentially. When information is written to memory, the encoded character is placed at a specific address. Main Memory Main memory (or system memory) is a temporary workspace that is active only while your computer is on. Any information placed in main memory is lost when you turn off your computer. Therefore, if you create or modify information, you must save the data to permanent storage, such as a diskette or hard disk. The main memory in your computer uses synchronous dynamic random access memory (SDRAM) modules for temporary storage of data and instructions. These SDRAM modules are also known as dual inline memory modules (DIMMs). SDRAM is volatile memory, which means that it must be constantly refreshed by an electric current. While the computer is turned off, no current is supplied to the DIMMs, so no data is retained in SDRAM. The DIMM connectors are located on the system board. For information about the type and amount of main memory (or System Memory) in your computer, view the System Summary screen displayed by the Configuration/Setup Utility Program. CMOS Memory Your computer also uses some nonvolatile RAM (NVRAM), also called complementary metal-oxide semiconductor (CMOS) memory, for storing configuration and setup information. Powered by a small battery, CMOS retains its contents while your computer power is off. CMOS maintains information about: Date and time Security features Power-management settings Storage devices Keyboard and mouse ISA legacy configuration information Plug and Play configuration information Port assignments I/O addresses and interrupts Other selectable features Flash Memory To store programs for startup procedures and other internal operations, some computers use read-only memory (ROM). These programs are encoded in ROM modules on the system board. ROM is nonvolatile memory, which means that it retains its contents when the computer is turned off. Generally, the contents of a ROM module cannot be modified. However, electrically erasable programmable ROM (EEPROM) modules (also referred to as flash memory) can be reprogrammed while they are in the computer. Microprocessors and Memory 3

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of memory, the computer can store over 1 000 000 characters of information.
The computer
organizes its memory by assigning an
address
to each byte as a point of reference.
The first
address is 0, and the addresses increase sequentially.
When information is written to
memory, the encoded character is placed at a specific address.
Main Memory
Main memory
(or
system memory
) is a temporary workspace that is active only while your
computer is on.
Any information placed in main memory is lost when you turn off your
computer.
Therefore, if you create or modify information, you must save the data to
permanent storage, such as a diskette or hard disk.
The main memory in your computer uses
synchronous dynamic random access memory
(SDRAM)
modules for temporary storage of data and instructions.
These SDRAM modules
are also known as
dual inline memory modules (DIMMs)
.
SDRAM is
volatile
memory, which
means that it must be constantly refreshed by an electric current.
While the computer is
turned off, no current is supplied to the DIMMs, so no data is retained in SDRAM.
The DIMM connectors are located on the system board.
For information about the type and
amount of main memory (or
System Memory
) in your computer, view the
System Summary
screen displayed by the Configuration/Setup Utility Program.
CMOS Memory
Your computer also uses some
nonvolatile RAM (NVRAM)
, also called
complementary
metal-oxide semiconductor (CMOS)
memory, for storing configuration and setup information.
Powered by a small battery, CMOS retains its contents while your computer power is off.
CMOS maintains information about:
±
Date and time
±
Security features
±
Power-management settings
±
Storage devices
±
Keyboard and mouse
±
ISA legacy configuration information
±
Plug and Play configuration information
±
Port assignments
±
I/O addresses and interrupts
±
Other selectable features
Flash Memory
To store programs for startup procedures and other internal operations, some computers
use
read-only memory (ROM)
.
These programs are encoded in ROM modules on the system
board.
ROM is
nonvolatile
memory, which means that it retains its contents when the
computer is turned off.
Generally, the contents of a ROM module cannot be modified.
However,
electrically erasable programmable ROM (EEPROM)
modules (also referred to as
flash
memory
) can be reprogrammed while they are in the computer.
Microprocessors and Memory
3