Adaptec 2740A User Manual - Page 20
Overview, The AHA-2740 Series of Host Adapters
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1 Overview This user's manual provides information on how to install and configure the AHA™-2740 and AHA-2742 single-channel, and the AHA-2740T and AHA-2742T TwinChannel™ EISA-to-Fast SCSI host adapters in an EISA computer system. The AHA-2740 and AHA-2742 support a single SCSI channel (SCSI Channel A), while the AHA-2740T and AHA-2742T support Adaptec's TwinChannel (SCSI Channel A and SCSI Channel B) architecture. Procedures for all adapters are the same except when regarding the on-board floppy controller on both the AHA-2742 and AHA-2742T. In this manual, the AHA-2740 and AHA-2742 are referred to jointly as the AHA-2740/2742 host adapter; the AHA-2740T and AHA-2742T are referred to jointly as the AHA-2740T/2742T host adapter. Cumulatively, all four host adapters are referred to as the AHA-2740 Series. The AHA-2740 Series of Host Adapters The AHA-2740 Series provides a high performance connection between the EISA (Extended Industry Standard Architecture) bus and the SCSI (Small Computer System Interface) bus. The AHA-2740 Series is a bus master device that transfers data into host memory at burst rates of 33 MBytes/sec. These transfers are generally 32 bits wide, except when transferring data into 8- or 16-bit memory. Bus mastering minimizes host CPU overhead, since the AHA2740 Series has an on-board sequencer (SCSI PhaseEngine™) that allows it to independently manage data transfer between SCSI devices and the computer system memory, without requiring the involvement of the CPU. This is the highest performance type of data transfer available for the EISA bus in multi-tasking operating systems. Adaptec AHA-2740 Series User's Manual Stock Number: 510381-00 / Rev. C (Page 1-3) Print Spec Number: 491709-00 Rev C Current Date: 9/1/93 ECN Date: 9/14/93 1-3