Adaptec AHA-2742T User Manual - Page 115

AHA-2740 Series User's Manual Programmed Input/Output A method of data transfer in which the host microprocessor transfers 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, connected 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 separate SCSI bus. Glossary-10 Adaptec AHA-2740 Series User's Manual Stock Number: 510381-00 / Rev. C (Page G-10) Print Spec Number: 491709-00 Rev C Current Date: 9/1/93 ECN Date: 9/14/93