Enhanced Mode Firmware - Adaptec AHA-1740A Technical Reference Manual

EISA-to-Fast SCSI Host Adapter
The host adapter dequeues on a first in, first out (FIFO) basis for each target/LUN
combination. However, due to the optimization algorithm used by the host adapter, a
task may sometimes be started earlier in spite of its late entrance in the queue on
multiple target/LUN systems. Task queuing should not be used where changes in the
order of command execution may cause data integrity failures.

Enhanced Mode Firmware

The Enhanced Mode is an interface architecture which allows the AHA-
1740A/1742A/1744 to take full advantage of the EISA bus facilities. It utilizes a dis-
tinct hardware interface control logic, implemented in the AIC-575 device. This
permits features such as full 32-bit addressing and the entire EISA register set to be
used. This mode is not compatible with older versions of the ASW-1400 series of soft-
ware managers.
The following levels of manager revision are capable of operating with the AHA-
1740A/1742A/1744 in Enhanced mode:
ASW-1410 v3.0 and later (ASPI DOS Manager)
ASW-1420 v1.3 and later (LADDR SCSI Support for OS/2
ASW-1440 v3.0 and later (ASPI Manager for Novell NetWare
ASW-1450 v1.0 and later (SCSI Manager for SCO UNIX
In order to use the Enhanced Mode, the AHA-1740A/1742A/1744 must be correctly re-
configured. Use the EISA Configuration Utility (EISA) that came with your EISA sys-
tem and the EISA configuration files on the ASW-C174 diskette provided with the
AHA-1740A/1742A/1744. The AHA-1740A/1742A/1744 are not capable of simultane-
ous operation in Standard and Enhanced Modes.
The firmware in this mode uses a different architecture to the Standard Mode. The
firmware is interrupt driven by events on the host and SCSI side. It uses only a sin-
gle mailbox, unlike the Standard Mode which uses up to 255. This does not result in
any bottleneck or performance impairment, due to the fast processor used on the
AHA-1740A/1742A/1744 and the servicing algorithm used.
Architecture
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