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From: aflundi@sandia.gov (Alan F Lundin)
Date: Fri, 16 Jun 1995 07:19:25 -0600
In-Reply-To: Bruce Evans <bde@zeta.org.au>
       "Re: HD Geometry dirty trick" (Jun 16,  1:38pm)
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To: freebsd-hackers@freebsd.org
Subject: Re: HD Geometry dirty trick
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On Jun 16,  1:38pm, Bruce Evans wrote:
> Subject: Re: HD Geometry dirty trick
>
> >> 	I've found that using "basic" geometry of 1023/64/32
> >> 	for SCSI HD with  1Gb capacity and just adjusting the first
> >> 	value for other capacities , one can get painless install .
> >> 	Foe example , if you install 4Gb HDD - we multiply 1023 by 4
> >> 	and use 4092/64/32 Geometry.
> >> 	For 300Mb SCSI disk we use (Int(1023/3.3))/64/32 and so on.
> 
> >Fine for Adaptec controllers, not so fine for NCR controllers that
> >like to tranlate >1G drives to xxxx/62/34, yes that is right 62/34!
> 
> I.e., 64/32 geometry works if it was the correct (BIOS) geometry all
> along.  Otherwise, it is unlikely to work.

What do you mean by "correct"?  I have a Fujitsu M2624 with
an Adaptec 1542B in my home machine and a Micropolis 2217
with a Buslogic Bt445S in my machine at work, and neither
have real geometries even in the ball park of xxxx/64/32,
yet xxxx/64/32 is what DOS fdisk gave and is the only geometry
of the several "reality based geometries" I tried that "worked"
with 2.0.5R.

I also have a Maxtor 7120a IDE drive that did not suffer
from the need for this trick.  I presume this is because
the CMOS contains the IDE geometry, but not the SCSI geometries.

--alan