Subj : My new* 486 (*=old)
To   : Ogg
From : Ben Collver
Date : Tue Feb 21 2023 11:01:15

  Re: My new* 486 (*=old)
  By: Ogg to Ben Collver on Mon Feb 20 2023 14:45:00

 BC> The disk is actually 13.6 GB but the BIOS can only see the first 4 GB.

 OG> I thought the BIOS report only referred to the RAM limit, not
 OG> HDD.

As i understand it the 4 GB RAM limit is imposed by the 32-bit architecture.

The 4 GB disk limit is imposed by the BIOS.  When i go into the BIOS setup and configure the hard disk, it recognizes it as a 4 GB disk even though the disk is physically labeled 13.6 GB.

This BIOS limit is mentioned in IBM's specifications.

"Up to 4GB of hard file capacity supported"

From:

<https://www.ibm.com/common/ssi/cgi-bin/ssialias
?appname=skmwww&htmlfid=897%2FENUS194-347&infotype=AN
&mhq=IBM%20Network%20Station%208361%20Series%20100
&mhsrc=ibmsearch_a&subtype=CA>

However, another IBM document implies this limit is per-disk.

Disk / Disk Controller

"PC 330: 8.4 GB (Two x 4.2 GB IDE disks)"

From a PDF titled "IBM PC 330 and PC 350 (6577 and 6587) - withdrawn"

BIOS disk limitations are described in the following post.

https://dfarq.homeip.net/bios-hard-drive-limits/

After reading this, i think that if i want to use more than 4 GB disk with FreeDOS, i would need to use a drive overlay.  Or i could partition the drive and dual-boot BSD or Linux, provided that i keep the boot partition below 4 GB.

-Ben

.