'386 Unix Wars

[Martin Weitzel]

In article <1659 at svin02.info.win.tue.nl> debra at svin02.info.win.tue.nl (Paul de Bra) writes:
>In article <94408977 at bfmny0.BFM.COM> tneff at bfmny0.BFM.COM (Tom Neff) writes:
>>...
>>Anyway, memory is so damn cheap these days.  My only beef is that, for a
>>UNIX release packing so many additional files, SVR4/386 doesn't have better
>>support for huge ESDI disks.  It chafes to have to throw away 100MB of
>>my Maxtor just to keep upder 1024 cylinders.  I would like to see this
>>addressed in a future rev.
>
>The 1024 cylinder limitation is not an AT&T invention.
>Complain to your vendor.
>AT&T Unix sVr3.2 and sVr4.0 (at least the beta i have seen)
>have no problems with drives with more than 1024 cylinders,
>without the need for funny translation procedures.
>I have used a CDC Wren V (383H) with 1224 cylinders and an
>Adaptec 2322 controller with both versions of Unix and never had
>any problem. ISC 2.0.1 (but i believe later versions have the same
>problem) decided (wrongly!) that my system would not support more
>than 1024 cylinders and would not let me access the last 200 cylinders.

This is NOT so.

The system on which I just compose this article runs with a CDC Wren V
(383H), a WD 1007V-SE2 ESDI controller and ISC 2.2. and it ran with
ISC 2.0.2 until Oct. 1990. I can use ALL of the disk WITHOUT any funny
translation from the controller (which in fact would support this, but
I decided not to use it for several reasons).

There are a few things you should remember (note that fdisk-partitions
here refer to the partitions you create with `fdisk', while UNIX-partition
refer to the ones you - or the installation procedures - creates with
`mkpart'):

      - Be sure to physically format ALL of the disk before you install
	UNIX. Either the disk manufacturer supplies special software for
	that or you can use the formatter in the controller's firmware.
	(For the WD 1007V-SE2 you call this formatter from the DOS
	debug command with `G=CC00:5' but the location may also depend
	on some jumper settings of the controller.)
	
      - When you partition your disk with fdisk, the maximum number
	of cylinders you can specify is in fact 1023. This doesn't hurt
	as long as you place the fdisk-partition(s) you want to use
	with DOS first and the fdisk-partition you plan to use with
	UNIX has at least ~40 MByte within the first 1024 cylinders.

      - When the installation procedures of ISC ask you about the `real'
	disk size, give the CORRECT number here (or one less than that -
	I will not go into details but I have experienced problems when
	I tried to use the very last cylinder with ISC 2.0.2; the problems
	may be cured in 2.2 but I only specified 1222 cylinders for my
	disk when I installed 2.2, so I can't really say.)

      - Create the UNIX-partitions (ie. the SUB-partitions WITHIN the
	fdisk-partition you use for UNIX) so that the one which holds
	the root directory after booting (/dev/[r]dsk/0s1) does not
	extend behind cylinder 1023. (This is due to the limitation
	that the kernal is read in with the PC-BIOS after boot and the
	BIOS can not access parts of the disk behind cylinder 1023.
	Note that the chances are you may never have a problem even
	if you don't follow that recommendation - until, one day, you
	make a new kernal and it, or part of it, is accidentially
	placed behind the 1023th cylinder!).

      - The WD 1007V-SE2 (I know, not the controller in question, but
	the one I have the docs for) has several translation modes, and
	there are in fact TWO "non-translation" modes. But there is only
	one which lets you acces the disk behind cylinder 1024. The docs
	warn not to use this mode unless the disk has more than 1023
	cylinders and "...you are using a special driver or operating
	system..."%

Good luck.

%: I was in fact reluctant at first to use this mode, since I rather
consider MS-DOS a special operating system, while UNIX is the standard
for me :-)
-- 
Martin Weitzel, email: martin at mwtech.UUCP, voice: 49-(0)6151-6 56 83