Overview; The Aha-2740W/2742W/2744W Host Adapters - Adaptec AHA-2740W User Manual

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Overview

This document provides information on how to install and
configure the AHA-2740W, AHA-2742W, and AHA-2744W EISA-to-
Fast, Wide SCSI host adapters in an EISA computer system.
The AHA-2740W, AHA-2742W and AHA-2744W support 16-bit Wide
SCSI via a 68-pin cable. In addition, a 50-pin cable connector is pro-
vided to connect 8-bit SCSI devices. The AHA-2742W and
AHA-2744W contain an onboard floppy controller.
In this document, the AHA-2740W, AHA-2742W, and AHA-2744W
are referred to jointly as the AHA-2740W/2742W/2744W.

The AHA-2740W/2742W/2744W Host Adapters

The AHA-2740W/2742W/2744W provide a high performance con-
nection between the EISA (Extended Industry Standard Architec-
ture) bus and the Wide SCSI (Small Computer System Interface) bus.
The AHA-2740W/2742W/2744W is a bus master device that trans-
fers 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
AHA-2740W/2742W/2744W has an onboard sequencer (SCSI
PhaseEngine™) that allows it to independently manage data trans-
fer between SCSI devices and the computer system memory, with-
out requiring the involvement of the CPU. This is the highest
performance type of data transfer available for the EISA bus in
multitasking operating systems.
The AHA-2740W and AHA-2742W support only single-ended SCSI
devices, while the AHA-2744W supports only differential SCSI
devices. Most of the SCSI drives on the market today are single-ended.
WARNING:
Differential SCSI devices may be damaged if con-
nected to the single-ended SCSI host adapter bus; similarly,
single-ended SCSI devices may be damaged if connected to
differential host adapters.
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AHA-2740W/2742W/2744W User's Guide
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Current Date: 8/3/94
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ECN Date: 8/9/94
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Introduction
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