Adaptec PC/104 - Manual (Page 50)

4 4 PCM-3420 User's Manual
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DEVICE DRIVER
A software program that enables a PC to communicate with
peripheral devices such as fixed disk drives and CD-ROM drives.
Each kind of device requires a different driver. Device driver
programs are stored on a PC’s fixed disk and are loaded into
memory at boot time.
DIFFERENTIAL
A term referring to the electrical characteristics of the signals
used on the SCSI bus interface. Differential signals occupy two
conductors with a positive (+) and negative (-) polarity compo-
nent of the signal. This minimizes the effect of common mode
signal noise and allow the SCSI bus to operate reliably over
greater distances at a higher speed.
DMA (DIRECT MEMORY ACCESS)
A mechanism that allows hardware control of the transfer of
streams of data to or from the main memory of a computing
system. The mechanism may require setup by the host software.
After initialization, it automatically sequences the required data
transfer and provides the necessary address information.