Adaptec AHA-2740 User Manual page 115

AHA-2740 Series User's Manual
Programmed Input/Output
A method of data transfer in which the host microprocessor trans-
fers data to and from memory via the computer's I/O ports. PIO
enables very fast data transfer rates, especially in single-tasking
operating systems like DOS.
R
RAM
Random Access Memory. Memory of which any byte can be
accessed directly in a single memory cycle. Information can be
read from and written to the memory.
ROM
Read-Only Memory. Memory in which any byte can be read but
not written.
S
Scatter/Gather
A device driver feature that allows the host adapter to modify the
transfer data pointer so that a single host adapter transfer can
transfer to many segments of memory in a single transfer,
minimizing interrupts and overhead.
SCB
SCSI Control Block. The mechanism used in emulation mode to
transfer control information to and from the board.
SCSI
Small Computer Systems Interface. A bus interface standard that
defines physical and electrical characteristics for hardware
devices. SCSI provides a standard interface that enables many
different kinds of devices, such as disk drives, magneto optical
disks, CD-ROM drives, and tape drives to interface with the host
computer.
SCSI Bus
One or more SCSI peripheral devices and a host adapter, con-
nected by cables in a daisy chain configuration. The bus may
include both internal and external SCSI devices. In systems that
have more than one host adapter, each adapter has its own sepa-
rate SCSI bus.
Glossary-10
Adaptec AHA-2740 Series User's Manual
Stock Number: 510381-00 / Rev. C
Print Spec Number: 491709-00 Rev C
Current Date: 9/1/93
(Page G-10)
ECN Date: 9/14/93