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Re: i386 mbr problem, again

On Thu, 3 May 2001, Nick Holland wrote:

> Tim Newsham wrote:
> > 
> > > Try booting a Windows rescue diskette and running
> > >
> > > a:> fdisk /mbr
> > 
> > This fixed my problem.

> > Does this mean that before OpenBSD can be installed
> > on a system, there must already be a DOS MBR created
> > on the drive?  If so, this seems braindead.  Not
> > everyone installs OpenBSD/x86 over a former windows
> > installation.

I agree.

> In my experience, if you take a never-before-used drive, and do an
> OpenBSD install on it on a machine that fully recognizes the drive
> geometry, OpenBSD installs (and later boots!) just fine.

So I guess these drives have no MBR; is this just zeros at the start of
the disk?

> It seems to be when the drive has been used for other things in the
> past, or on machines which treat the drive geometry differently,
> things don't work quite right, and the (DOS) 'fdisk /mbr' fixes the
> problem.  Installing over an alternative OS actually may be related to
> the problem.

It seems like I have heard of using dd to zero out the first 512 bytes of
the disk as a work-around. But I also have heard that only the first 447
bytes should be zeroed. Does anyone have experience with this? (And does
nayone have any pointers to documentation or notes on working around this
problem without DOS fdisk?)

   Jeremy C. Reed