Subject: Re: NetBSD Hang after disklabel, xsm crash
To: None <root@garbled.net>
From: Joel Reicher <joel@panacea.null.org>
List: port-i386
Date: 07/30/1998 00:28:37
> This would be the correct way to do things..
> 
> Just a question of curiosity to everyone out there.. Why do you offset 63
> sectors into the disk?  I've never done that on any of my machines.. and it
> works just peachy..

>From the (very) little that I know, it's not 63 sectors, it's the first track,
and tracks are _typically_ 63 sectors.

It seems to be traditional for a lot of booting software to use the first
track for all sorts of things now. Even the latest os-bs beta uses it, so
leaving it free is generally safer. I think OS/2 also uses it for its boot
code, but don't quote me.

The other possibility is that NetBSD now uses it with the DOS/FDISK stuff,
but I'm not up to date with that stuff.

> If anything.. that would seem to me like a "bad thing" because you aren't
> starting and stopping on a cylinder boundary..

Drives stopped having a constant number of sectors per cylinder a while
ago and now go for constant data density instead, AFAIK. The geometry you
see is spoofed by the _drive_. Not even the controller really knows what's
going on, and so I don't think there are performance advantages to keeping
things on cylinder boundaries anymore, it's just "pretty".

There's every chance I'm very wrong though.

	- Joel