Date: Tue, 28 Nov 1995 17:27:01 +1100 From: Bruce Evans <bde@zeta.org.au> To: roberto@keltia.freenix.fr, wilko@yedi.iaf.nl Cc: FreeBSD-hackers@FreeBSD.org Subject: Re: Translation Adaptec 1542 versus NCR810 Message-ID: <199511280627.RAA14266@godzilla.zeta.org.au>
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>> Quick question: is the translation mode used by a Adaptec 1542A (32 hd, >> 64 sect or the other way around (I always forget)) the same as the one >> used by a NCR810 ? >I'm afraid not... Last time I installed a disk in a friend's machine with a >NCR, it used something like 33hd/63sect or 63hd/33 sect :-( I tried modifying the geometry for one of my (installed) drives on a BT445C the other day. It was easy to set up the following geometries without affecting the FreeBSD partitions (sd1s2-sd1s4). Even the DOS partition (sd1s1) worked according to chkdsk, but since it didn't have any files on it and the DOS BPB has the geometry in it, I wouldn't trust it. Method: run FreeBSD fdisk (fdisk -u /dev/rsd1) and change the "parameters to be used for the BIOS calculations", then answer `y' to all questions about changing the partitions, but hit return to accept the defaults. Reboot and the BT445C will report the changed geometry if the change is valid. I tried the following: 64 heads 32 sectors original 128 heads 32 sectors worked 256 heads 32 sectors BT445C thought it was 255 heads 32 sectors (?) 256 heads 63 sectors BT445C thought it was 255 heads 63 sectors 255 heads 63 sectors worked I'm now using 255 heads 63 sectors but I wouldn't expect all controllers to agree on this. The BT445C apparently uses similar guesses (based on the partition table) to FreeBSD to decide the geometry but it may have a better default (64/32?) when the partition table is empty. The geometry for IDE drives is almost as flexible. The following works for my 1993 AMI BIOS: Enter a physically and BIOSically possible geometry in setup (physical: H <= 16; BIOS: S <= 63). The BIOS is too old to support H> 16. Update the partition table as above to match the geometry. Bruce
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