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cached. However, only 512KB of this memory will be in the cache at any given
moment. Any main memory above 512MB could never be cached.
Closed and open jumpers
Jumpers and jumper pins are active when they are
On or Closed, and inactive when they are Off or Open.
CMOS
C
omplementary
M
etal-
O
xide
S
emiconductors are chips that hold the
basic start-up information for the BIOS.
The
COM port
is another name for the serial port, which is so-called because it
transmits the eight bits of a byte of data along one wire, and receives data on
another single wire (that is, the data is transmitted in serial form, one bit after
another). Parallel ports transmit the bits of a byte on eight different wires at the
same time (that is, in parallel form, eight bits at the same time).
DIMM
D
ual
I
n-line
M
emory
M
odules are a faster and more capacious form of
RAM than SIMMs, and do not need to be installed in pairs.
DIMM bank
DIMM banks are sometimes called DIMM sockets, because the
physical slot and the logical unit are the same. That is, one DIMM module fits
into one DIMM socket, which is capable of acting as a memory bank.
DMA
D
irect
M
emory
A
ccess channels are similar to IRQs. DMA channels allow
hardware devices (like sound cards or keyboards) to access the main memory
without involving the CPU. This frees up CPU resources for other tasks. As
with IRQs, it is vital that you do not double up devices on a single line. Plug
and Play devices will take care of this for you.
In
Doze mode
, only the CPUs speed is slowed.
DRAM
D
ynamic
RAM
is a widely available, very affordable form of RAM
which has the unfortunate tendency to lose data if it is not recharged regularly
(every few milliseconds). This refresh requirement makes DRAM three to ten
times slower than non-recharged RAM such as SRAM.
EDO RAM
(
E
xtended
D
ata-
O
ut
RAM
) speeds access to memory locations by
assuming that memory addresses are static: the next time it looks for a bit of
data, it will be at the same spot, or one nearby.
EEPROM
Electrically Erasable Programmable ROM, also called Flash BIOS, is a
ROM chip which can, unlike normal ROM, be updated. This allows you to keep
Appendix
Glossary
