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CDROM works, but can't really boot from it

U

Uniballer

Experienced Member
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Apr 3, 2014
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I have a 486 system with AWARD MODULAR BIOS v4.50G with an ID of 09/08/94-OPTI-802G-2C4UKD01-00 (I know it isn't quite 20 years old yet). I don't expect a BIOS this old to be able to boot from an IDE CD, but using the PLOP 5.0.14 boot manager I can get the UBCD 5.25 CD to boot to the menus. But anything I have tried to run from the menu fails to boot (e.g. Memtest86+, MHDD32). Likewise, I can't get FreeBSD to boot from the CD. If I boot the system from a hard disk prepared on another machine it boots up fine, and the CD works properly. Is this failure to boot a BIOS issue, i.e. the initial boot code on the CD makes BIOS calls that don't work? Or do you think it is something else?
 
gslick said:
According to the Wikipedia page the El Torito Bootable CD Specification was announced in November 1994. If the date of your BIOS is September 1994 my guess is that it would be lacking any support for bootable CD-ROMs.

http://en.wikipedia.org/wiki/El_Torito_(CD-ROM_standard)

The “El Torito” Bootable CD-ROM Format Specification Version 1.0 is dated January 25, 1995

http://download.intel.com/support/motherboards/desktop/sb/specscdrom.pdf
Click to expand...
He is using a bootload to chainload the CDROM.

Make sure the software you are trying to boot supports 486 CPUS
 
I checked the boot sector source code for FreeBSD 6.4 and there is nothing incompatible with a 486 CPU, but there are int 0x13 BIOS calls (as well as numerous other BIOS calls). I have not looked but assume that the ISOLINUX code that boots to the UBCD menu does not use BIOS calls to get the job done (does that make sense?).
 
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