*BSD News Article 71139


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From: j@uriah.heep.sax.de (J Wunsch)
Newsgroups: comp.unix.bsd.freebsd.misc
Subject: Re: IDE Hard Disk questions
Date: 15 Jun 1996 19:02:27 GMT
Organization: Private BSD site, Dresden
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ganderso@ida.org wrote:

> I recently acquired a new, 2.1Gb IDE hard disk that I would like to install 
> FreeBSD 2.1.0-RELEASE onto.  The question is, in the BIOS setup, should I
> use "LBA" which forces a drive geometry that is different from the actual
> geometry, or "NORMAL" with the correct drive geometry.

Hmm, i'm sounding like a broken record here...

There's no such thing like ``operate with the correct drive geometry''
for all modern drives.  Every and all of them are *always* translated,
it's only that you've got a choice about which translation to use.

If the drive is FreeBSD and FreeBSD only, you can select any geometry
you want when using the ``dangerously dedicated'' mode.  Select A)ll
FreeBSD in the partition editor, and answer the next question about
the way ``compatible with other systems'' with ,,No''.  This will
place the BSD bootstrap in place of the MBR, and the only requirement
for the BIOS then is to have at least 15 sectors per track.  Of
course, this won't leave any room for a boot manager, so don't use it
on the first drive of a multi-boot machine.  (``Dangerously
dedicated'' :)

> On a related note, can anyone provide any relevant insights on
> performance differences between an EIDE drive on a PCI-based
> controller versus a SCSI drive,...

FreeBSD doesn't support EIDE DMA modi, so an EIDE machine will
basically suffer from a higher CPU load.  This makes an IDE machine
with a i586/166 appear slower than an i586/100 with a good SCSI
subsystem when it comes to higher CPU loads like a large compilation.

Btw., the differences between similar drives (same manufacturer, same
drive, but different interface) are not that high.  So if your IDE
disk is significantly cheaper, it's also risky to be crap.

-- 
cheers, J"org

joerg_wunsch@uriah.heep.sax.de -- http://www.sax.de/~joerg/ -- NIC: JW11-RIPE
Never trust an operating system you don't have sources for. ;-)