XENIX 2.2.3 and >1024 h.d. cylinders: possible?
Ronald Khoo
ronald at ibmpcug.co.uk
Thu Sep 14 10:47:14 AEST 1989
In article <5364 at tank.uchicago.edu> goer at sophist.UUCP (Richard Goerwitz) writes:
>
>Re big Wren drives > 1024 cylinders
>
>You can always use the option, available via your WD1007 controller,
>of formatting the drive as usual, but having the controller make it
>appear to the operating system as though there were 63 sectors per
>track and a whole lot less tracks.
Beware that there are several pitfalls here:
1) invoking sector translation can have a performance hit.
After all, mkfs/fsck -s organises the free list assuming
the actual shape of the disc is what you tell it is.
These assumptions can go horribly wrong when you invoke
peculiar translations like the 1007 can do. It'll WORK,
but you'll have your disc seeking all over the shop.
Can you say Sloooooow? I thought you could...
2) there can be a confusion when you mention 63 sector mode--
there is a NON-TRANSLATED 63 sector mode where each sector
is 256 bytes in size. (You did say WD1007 ESDI, right?)
You definitely DO NOT want to low-level format the disc
in this format :-)
3) Hey, why muck around? Xenix does *not* have a 1024
cylinder limit. Try it and see--just make sure that
in the early part of the disc initialisation process,
that you OVERRIDE the disc parameters. This causes
/usr/lib/mkdev/hd to perform a dparam -w which
lets you use a disc of any reasonable shape, even if your
BIOS does not have a corresponding drive type number.
Just use any type number with the same number of heads,
and a lower cylinder count to enable the boot sequence
to operate properly. No hassle. Honest. I do it alla time :-)
--
Ronald.Khoo at ibmpcug.CO.UK (The IBM PC User Group, PO Box 360, Harrow HA1 4LQ)
Path: ...!ukc!slxsys!ibmpcug!ronald Phone: +44-1-863 1191 Fax: +44-1-863 6095
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