EAHA(4) BSD Programmer's Manual EAHA(4)NAMEeaha - Adaptec 1740A/1742A EISA SCSI host adapter driver
SYNOPSIS
eaha0 at eisa?
DESCRIPTION
The eaha driver is a software interface to the Adaptec AHA-1740,
AHA-1740A and AHA-1742A host adapters for the Small Computer Systems In-
terface (X3.131-1992) bus. The driver assumes that the card has been
programmed for `enhanced mode' operation, which permits it to take advan-
tage of EISA features; in the other mode, `standard mode', the card be-
haves like an AHA-1542B (see aha(4)). To program the card for enhanced
mode operation, you will need to run the manufacturer's EISA Configura-
tion Utility for your machine under DOS, load the Adaptec configuration
files (if they weren't provided by the manufacturer), and set all the
relevant card parameters to their enhanced mode defaults.
The Adaptec cards provide automatic SCSI protocol handling, in which the
driver just sends a SCSI Command Descriptor Block and the SCSI protocol
state is managed on-board. They provide parallel operations, using a
`mailbox' protocol which allows the host to send several operations that
the board will schedule automatically. The cards also support EISA bus
master DMA, using an on-board DMA controller that takes advantage of EISA
bus bandwidth and does not use any ISA DRQ resources. The cards can pro-
gram their own IRQ; the driver selects an available IRQ value from the
set of 9, 10, 11, 12, 14 or 15 and programs it when the card is config-
ured. The Adaptec firmware offers scatter/gather mapping, a technique
for handling transfers out of virtual memory that works by providing the
card with a map of the physical addresses in a virtual region. Unlike
the AHA-1542B, the AHA-1742A supports full 32-bit physical addresses.
Two SCSI features supported in firmware are automatic synchronous SCSI
protocol negotiation, which can identify SCSI peripherals that support
high-speed operation and match transfer speeds, and automatic con-
nect/disconnect bus control, which allows the host adapter to disconnect
from long-running operations such as seeks or rewinds and to connect to
other operations on other targets while waiting for the original opera-
tion to reconnect. The AHA-1742A differs from the AHA-1740A in providing
an on-board floppy controller which is handled using a standard floppy
interface (see floppy(4)).
The eaha driver is designed to be used as a machine-dependent back end
for machine-independent SCSI pseudo-devices (see sd(4), st(4)).
Booting from a SCSI disk attached to an Adaptec host adapter requires
boot code with knowledge of the host adapter. A SCSI disk boot block
named eahaboot and a 14-sector boot named booteaha must be installed us-
ing disksetup(8) on a SCSI disk in order to boot from the Adaptec inter-
face. The Adaptec card simulates the BIOS interface for a standard PC
hard disk for the purpose of booting. The card uses a set of specific
drive selection criteria to choose a default boot disk; these parameters
are set using the EISA Configuration Utility.
BOOT PARAMETERS
There are now parameters which are configurable from boot(8) with the
-parm command. Typically these commands would be added to boot.default(5)
though they can be set at the ``boot:'' prompt.
Many of the parameters take as an argument one or more target ids. The
following are permissible arguments to these parameters:
t0 target 0.
target0 target 0.
t1 target 1.
target1 target 1.
t2 target 2.
target2 target 2.
.
.
.
t6 target 6
target6 target 6
t7 target 7
target7 target 7
all targets 0 through 7
none no targets
The following parameters take a list of target specifiers as an argu-
ment(s):
single_lun
For these targets only look at lun 0.
-parm eaha* single_lun=none #default
-parm eaha* single_lun=all
skip_targets
These targets will not be probed at boot. Examples:
-parm eaha* skip_targets=none #default
-parm eaha0 skip_targets=target5 #Don't probe target 5
The following parameter takes a numeric value as an argument:
reset_delay
This is used to control the number of seconds of delay
which is inserted after the SCSI bus is reset at boot time.
-parm eaha* reset_delay=5 #default
-parm eaha* reset_delay=1 #1 second reset delay
-parm eaha* reset_delay=0 #no delay after reset
SEE ALSOaha(4), sd(4), st(4)BUGS
The eaha driver should be configured as late as possible so that it won't
choose an IRQ that some other card with a fixed IRQ needs.
The default synchronous transfer rate can be too high for some SCSI de-
vices. If trouble occurs, try lowering it with the ECU.
BSDI BSD/OS August 8, 1997 2
