[syslinux] isolinux not booting - old 486 with SCSI CD writer

[Bruce Robson]

I am trying to install Debian Linux on an an old Intel Classic R+ computer that
uses an internal Yamaha SCSI CD writer model CRW8424S connected to an Adaptec
ISA SCSI card (I think its a 1542CP). The CD writer is is the only device
connected to the SCSI card. The computer has one hard drive connected to the
on-board IDE interface, a 1.44MB 3 1/2 inch floppy and a 1.2MB 5 1/4 inch floppy.
The hard drive is 1.6GB and contains EZ-Drive as the BIOS only supports drives
up to 500MB approx. However, EZ-Drive only loads when booting from hard drive.

During the boot the following messsages were output by the Adaptec BIOS
   Press ^A for SCSISelect(TM) Utility!>>>
SCSI ID #1 - Yamaha CRW8424S
A BOOTABLE CD-ROM IS DETECTED IN YOUR CDROM DRIVE.
The boot sections on your bootable CD-ROM are:
       0. DEFAULT ENTRY
YOUR CD-ROM DRIVE IS INSERTED AS - DRIVE D:(81h)
BIOS Installed Successfully.

Once the BIOS had finished I received the following messages
ISOLINUX 3.51 2007-06-10 isolinux: Loading spec packet failed, trying to wing it.
...
isolinux: Found something at drive = 81
isolinux: Failed to locate CD-ROM device; boot failed.
See http://syslinux.zytor.com/sbm for more information.

The Microsoft Windows 98SE installation CD does boot on this computer.

I downloaded syslinux-3.61 and made a CD that used the debug version. The messages
from this were
ISOLINUX 3.61 2008-02-03 Copyright (c) 1994-2008 H. Peter Anvin
isolinux: Starting up, DL = 01
isolinux: Loading spec packet failed, trying to wing it...
isolinux: Trying BrokenAwardHack first ...
isolinux: BAH: Original Int 13 vector : DC002343
isolinux: BAH: FAILURE
isolinux: Found something at drive = 81
isolinux: Failed to locate CD-ROM device; boot failed.
See http://syslinux.zytor.com/sbm for more information.

Having found the “El Torito” Bootable CD-ROM Format Specification
http://www.phoenix.com/NR/rdonlyres/98D3219C-9CC9-4DF5-B496-A286D893E36A/0/specscdrom.pdf
I made changes to isolinux.asm to display the spec packet and accept drive 81h.
I've attached a diff of my changes.

Using the changed isolinux (again debug version) the last few lines were
isolinux: Found something at drive = 81
   13 00 00 00 00000047 01 00 0000 0000 0004 57 A0 3F 00
isolinux: Loading main image from LBA = 00000048
isolinux: Sectors to load = 0006

The computer then sits there continuously accessing the CD drive.
The computer did reboot when Ctrl-Alt-Del was pressed.

I tried again. This time I ejected the CD when the computer was
continuously accessing the CD drive. This resulted in the following message
isolinux: Disk error 80, AX = 420081

I don't have time to continue at the moment. Does any one have any good
references on the BIOS functions used or suggestions as to how to continue
when I do have time.

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