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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
Dual In-line Memory Modules 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
Direct Memory Access 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 CPU’s speed is slowed.
DRAM
Dynamic RAM is a widely available, very affordable form of RAM
which has the unfortunate tendency to lose data if it is not recharged regu-
larly (every few milliseconds). This refresh requirement makes DRAM three to
ten times slower than non-recharged RAM such as SRAM.
EDO RAM
(Extended Data-Out RAM) speeds access to memory loca-
tions 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 up with changes in the BIOS programs without having to
buy a new chip. TYAN’s BIOS updates can be found at http://www.tyan.com/
html/drivers.html
ESCD
(Extended System Configuration Data) is a format for storing
information about Plug and Play devices in the system BIOS. This informa-
Chapter 6
System Resources
