A source of great confusion to many people is the question of which partitions are bootable
on large drives. The question arises in deciding how big to make the OS/2 boot partition,
where to place the maintenance partition, and several other issues. The matter is made
even worse because no "standard" answer seems to work in every case. During the course
of a discussion on the subject on an OS/2 Forum one knowledgeable user gave one of the best and
most complete answers to this problem I have ever
seen, and he has given me permission to reprint his reply. Here it is:
Just wanted to make a quick comment about boot limitations.
The limitation is not an absolute size such as 512 MB or 2 GB or even 8 GB. It's the
number of cylinders, which is 1024. However, and motherboard BIOS's have evolved, the
size represented by 1024 cylinders has changed. Lately, using LBA addressing means that
1024 cylinders can now address up to 8 GB of space on a hard disk. So, whether you can
boot from 512MB, 2GB or 8GB is more a function of the BIOS on your motherboard than
anything to do with the system.
OTOH, because of a bug in older versions of ibm1s506.add (this is the IDE bus driver for
the system) it was not possible for os2 to see more than 2 GB of disk space. This did not
matter then as there was no such thing as a hard drive that large; the bug only got
discovered when the new crop of large hard drives started becoming available. Because of
this, if you don't have a fixed ibm1s506.add on your system, you cannot practically boot
from past 2GB because warp couldn't see past 2GB. However, if you have an old motherboard
with a large hard drive, you will still not be able to surmount its limitations wrt booting
no matter what version of ibm1s506.add you are using; so if you have an old 486 motherboard
and are using a 13 GB drive in it, you will have to install warp into the first 512 MB in
order to boot it. If you're using later versions of ibm1s506.add or dan1s506.add, after
the system boots warp will be able to see and address the rest of the disk as another
partition. [Copyright (c) January 2000 by Jack Troughton. Reprinted with permission.]
In a subsequent post, Jack summarized the above material as follows:
New computer with a big drive:
You can boot as long as the boot partition resides completely within the first 8 GB of
the drive. You will have to get a new driver for your IDE interface (ibm1s506 OR dan1s506)
in order to see beyond the first 2 or 4 GB (2 if warp 3, 4 if warp 4).
Old computer with big drive:
Depending on the motherboard, your boot partition will have to entirely reside either
within the first 512 MB or 2 GB of the disk. If you want to see past 2 or 4 GB, you will
have to get a new IDE driver. However, you won't have to get ontrack or anything like that
in order for warp to see the whole drive. Since it replaces the BIOS code that controls the
drive as it boots, it can see the whole drive whether or not the motherboard's BIOS can.
That's the nutshell view of the issue...
[Copyright (c) January 2000 by Jack Troughton. Reprinted with permission.]
