How to enable the Adaptec AHA-1542C ISA SCSI card in Red Hat Linux 7.2

By Phil Jones (pjls16812 [at] blueyonder.co.uk)

Introduction

This describes how I successfully got an Adaptec AHA-1542C Small Computer System Interface (SCSI) Industry Standard Architecture (ISA) card working with Red Hat Linux 7.2. It explains how to view and access an external SCSI hard disk connected to the AHA-1542C. I assume you have just one SCSI card, and one external SCSI hard disk.

Overview

The good news is Red Hat Linux 7.2 has all the drivers needed for the card pre-installed. The bad is the AHA-1542C is a non plug-and-play ISA card. You need to disable certain plug-and-play facilities on your motherboard. It's necessary because plug-and-play gets in the way of the Linux driver for the AHA-1542C.

Procedure

Installing the card

Turn off the computer. Find a vacant ISA slot and push the card in.

Setting the external drive's SCSI ID to 0

You need to set the external drive to SCSI ID 0 because the SCSI card will expect to find the drive there. On the Microp 3321 which I have, the SCSI ID of the drive can be changed by pushing a little button at the back of the drive using a pencil. There's two buttons and a counter which indicates the selected SCSI ID.

Connecting the external drive

Connect the drive to the AHA-1542C using the appropriate cable.
Turn on the drive. Remember the SCSI drive needs to be on before the computer.

Checking the card's IRQ

Turn on the computer.
Look at the BIOS messages.
You should see messages from the Adaptec AHA-1542C.
This screen shows the AHA-1542C is available in the system! Press Ctrl + A when prompted.
You will see the SCSI card selection screen.
The adapter is on port address 334. If you select one of the other ports, you will be told there is no SCSI card on that port. Press Enter to configure the adapter on port 334.
Select View Adapter Settings and press Enter.
You will see the adapter settings screen.
Notice the IRQ the card is on. In all likelihood it will be set to IRQ 11.
Press F6 to load the default settings for the card. The default settings are fine.
Press Escape to exit the SCSI Select Utility and reboot when prompted.

Disabling PnP on the card's IRQ

When the motherboard BIOS messages comes up again, press the appropriate key to enter BIOS Setup. For example, if it says 'Press Del to enter Setup', go ahead and press the Delete key.
Note that some PCs such as Compaq need special disks for BIOS setup. Corporates tended to like Compaq machines because they were more difficult for employees to fiddle with. If you have one of these machines, you'll need to download the appropriate utilities from the manufacturer.
You will see the motherboard BIOS utility screen.
Select PNP/PCI Configuration.
Find the IRQ that the AHA-1542C wants to use and set it to Legacy ISA. For example, set IRQ 11 to Legacy ISA. This means, disable plug-and-play on IRQ 11.
Save changes and exit.

Loading Linux and the kernel module for the SCSI card

Let Red Hat Linux 7.2 boot up.
Log in as root.
Enter this command:
modprobe aha1542
If you get the command prompt back again without any error messages, congratulations, the driver loaded! Enter this command:
dmesg

You should see the following lines at the end of the output:


SCSI subsystem driver Revision: 1.00
Configuring Adaptec (SCSI-ID 7) at IO:334, IRQ 11, DMA priority 5
scsi0 : Adaptec 1542
  Vendor: MICROP    Model: 3221-10MZ 1128RQ  Rev: HZRQ
  Type:   Direct-Access                      ANSI SCSI revision: 02

This means the Adaptec AHA-1542C was found at port address 334, IRQ 11, DMA 5. The external drive is now available as the device /dev/sda.

Examining the external drive's partitions

Enter this command:
fdisk /dev/sda
Press P to view the partition table on the drive. If the drive is Macintosh formatted, the list of partitions will be empty, this is normal. Press Q to quit fdisk.

Examining the raw data of the external drive

Since the external drive is available as a file, you can pass it through the 'more' pager to see the raw data on the disk. Enter this command:
more /dev/sda
The output may not be very useful but you might find it interesting to look at. Press Q to quit the pager.

Mounting partitions from the external drive

First create a directory where you want the files on the external drive to appear:
mkdir /mnt/scsi
Assuming there is one big Windows 9x type partition on the external drive, use this command to put its files in the directory /mnt/scsi:
mount -t vfat /dev/sda1 /mnt/scsi

If the external drive is Macintosh formatted

Load the Macintosh file format support module:
modprobe hfs
Mount the drive. For example, this command will mount /dev/sda and put its files in /mnt/scsi directory:
mount /dev/sda /mnt/scsi
Remember you can specify any directory you want in place of /mnt/scsi.