Difference in slice numbering FreeBSD 4.x vs. 6.x?

[Torfinn Ingolfsen]

Hi,

Yes, this is a strange question; is the slice numbering in FreeBSD 4.x
different from that in FreeBSD 6.x?
I'm talking about for fdisk(8), boot(8) and loader(8).
Background: I have this old laptop (a HP OmniBook 5500CT). I replaced
the tiny (1.2GB) hard drive in it with a 20GB hard drive.
I installed FreeBSD 4.11-RELEASE on it, using fdisk to partition the
disk in two. 4.11-R installed on slice1, ie. root on /dev/ad0s1a.
All was well.

Now, the story:
Then I decided to install FreeBSD 6.0-RELEASE on the second half of the
disk, but it didn't work out of the box. To make a long story short, it
turned out that the PCCard controller / slots wasn't detected properly,
and as this laptop doesn't have a cd-rom drive, I just took out the hard
drive, mounted a 2.5-to-3.5 inchadapter on it and put it into another
machine. This machine had a cd-rom, and it installed FreeBSD 6.0-R on
the second slice without a problem.
I even testedt that it would boot both slices (4.11-R or 6.0-R) on that
machine, it did. On this machine, 4.11-R was on slice 1, and 6.0-R on
slice 2.

Now, I took the hard drive out and put it into the laptop again.
Mahor problem - it wouldn't boot at all. A not-so-quick boot with the
floppies (3 floppies for boot, plus the fixit floppy) later, I ran fdisk
on ad0.
Much to my surprise, the twor FreeBSD installations had now moved to
slice 3 and slice 4.
4.11-RELEASE on slice 3 and 6.0-RELEASE on slice 4.

I am utterly amazed by this. What has happened?
-- 
Yours,
Torfinn Ingolfsen,
Norway