Adaptec 1742A User Manual

Contents

Chapter OneOverviewThis User Guide provides software installation information forthe Adaptec AHA-1740A, 1742A, and the 1744 EISA-to-fast-SCSIbus master host adapters. Cumulatively the cards are referred toas AHA-1740A/1742A/1744 in this guide. The Adaptecadl.exedownload utility and theASW-C174 andASW-M174 softwarepackages are described, as well as available software support.General Product InformationThe AHA-1740A/1742A/1744 provides a high performance connec-tion between the EISA (Extended Industry Standard Architec-ture) bus and the SCSI (Small Computer System Interface) bus.The AHA-1740A/1742A are single-ended SCSI host adapters thatsupport single-ended disk drives. Single-ended host adapters anddevices can support cable lengths of up to 6 meters (about 18feet). Most of the SCSI drives on the market today are of thistype. The AHA-1744 Host Adapter is a differential SCSI hostadapter that supports differential type SCSI devices. The use ofdifferential SCSI drives and adapters allows the SCSI cablelength to be up to 25 meters in length (about 75 feet). Other thanthis basic difference, and other slight differences discussed in thisdocument, the AHA-1740A/1742A/1744 are installed and operateidentically.The AHA-1740A/1742A/1744 is a bus master device and transfersdata into host memory at burst rates of 33 MBytes/sec. Thesetransfers are generally 32 bits wide, unless transferring data into8- or 16-bit memory. This form of transfer is known as bus mas-ter DMA (Direct Memory Access). Bus mastering minimizes hostCPU overhead, since the AHA-1740A/1742A/1744 has an on boardprocessor to transfer data directly to memory. This is the highestperformance type of data transfer available for the EISA bus inmultitasking operating systems.1-1