3b2 Questions - Answers Appreciated

[Philip A. Gross]

In article <7455 at batcomputer.tn.cornell.edu>, hurf at batcomputer.tn.cornell.edu (Hurf Sheldon) writes:
[...stuff deleted...]
> 
> 	Questions:
> 
> 	1; Is there a way to make a bootable floppy system
> 	   so we can try to salvage systems that are having a problem
> 	   without doing the 'Essential utilities, partial restore'
> 	   route? Essentially a kernal with mount, fsck, makedev
> 	   etc so we can boot, fsck the hard drive and mount it.

While the answer to this question is "yes" you can create a diskette
with a bootable file system, there is essentially (pardon the pun)
an easier way to approach this problem without going to the trouble
of making one.

The Essential Utilities Diskette 1 for your AT&T Sysv3.1 is a mountable
filesystem.  Now there is a little known way in which to gain access
to a somewhat restricted shell when you boot on this floppy.  What you
need to do is to bring your maching to FIRMWARE MODE and enter unix
as the program to execute and indicate device 0, the floppy diskette
as your boot device.  This you are probably familiar with.  After much
twitling (sp) of thumbs, you will finally be presented with the
familiar menu where you have the option to do an upgrade, full restore,
partial restore, or quit.  Well instead of typing any of the suggested
options, type:

magic mode

the computer will then respond:

POOF!

(I kid you not) and you will note that you now have an additional
option "shell".  Enter:

shell

and you will be presented with a '#' sign prompt.  There also exist
other hidden options which can be found by examining the installation
program.  I believe it is /etc/rc on the floppy, you can double check
this by examining the /etc/inittab file on the floppy to see what it
runs on bootup.  Nevertheless, you will be working in a restricted
environment.  For example, you will not have 'vi'.  'Ed' and 'cat' 
will have to do (I can't even recall if ed is even supplied).  Also 
you will find that you don't even have 'ls', for this you will have
to use 'echo *' in order to get directory listings.  In order to
find out what devices, etc are available to you, you can type 'set'
to list the environment variables which have been defined.  Several
things such as 'mount' have been defined as functions and are not
available in the normal format.  You may want to hack with this on
a system when you are not under a pressure situation.

[...stuff deleted...]
> 	3; Hard drive questions;
> 		a; Do the 3B2's use a standard configuration hard drive?
> 		   ie: What will fit and how much is it?

The older 3B2's, generally 300s, 310s and most 400s use the ST506
interface.  The more recent models of the 400 and on up now use ESDI
drives.  As for size, for one in order to use a non-AT&T supplied
drive, you need to have access to the low level formatting programs.
These are found on releases of what is called DEVTOOLS and more
recently IDTOOLS diskettes.  These diskettes, like the Essential
Utilities Diskette 1 are bootable filesystems on the floppy.
If you use the DEVTOOLS diskette, the largest I have ever been able
to format is to ~72Mb.  Now with the IDTOOLS I have been able to
coerce a couple of PRIAM's and MAXTOR's to format to ~190Mb (1224
cylinders).

> 
> 		b; What does it take to mount a second hard drive either
> 		   in the 3b2 chassis or outside. We have a couple of
> 		   spare 30meg drives that we would like to put in
> 		   place of the floppies on a couple of systems. Can that
> 		   be done? - It looks like the cables to the hard drive
> 		   port in the back could just be pulled off and connected
> 		   to another drive, except for the little 2 wire cable
> 		   from the port to the internal drive. Also what drive
> 		   selects to use?

To mount a drive externally, not a great deal except money.  You will
need an external cabinet of sorts one out of a PC magazine works with
one of our machines (don't plan on AT&T supporting it) or you can
purchase an XM with the appropriate cables in order to connect the
drive externally.  As far as cables go for the external disk, we use
a simple PC hard disk ribbon cable, but you must keep the distance to
a minimum or you will have problems with the hdelogger reporting
hd errors that do not really exist.  AT&T does sell special cables for
running externally which are shielded, but the price is mucho $$$.
I believe the 20 pin external cable is about $80.00 and the 34 pin
external is ~$175.00.  As far as installing a hard disk in place of a
floppy, you may be able to get away with that but you will have to
reconfigure the ends of the data and control cables to have card
edge connectors instead of what is supplied.  The 'little 2 wire'
cable that you speak of is simply having the internal drive make
use of the resistor pack which is on the external port "board".
The internal drive, the root drive, is selected as drive 0 and the
other drive is selected as drive 1.  You will need to remove the
2-wire cable and install the resistor pack on whichever drive is
at the end of the "chain".

> 
> 		c; Is there a place that rebuilds the drives at an effective
> 		   cost?

Don't know, but please let me know if you find one.  We have a
72Mb CDC Wren II that has lost its mind and needs a bit of
"psychological" help in order to get it to work again.

> 
> 		b; Is there an independent repair facility for 3b2 
> 		   board level repairs?
> 
> 		c; Are there any hardware manuals available for the 3b2/310?

Again, let me know if you find these answers.  I have learned what I have
through 3 years of trial & error & intense hardware/software hacking.

> 		c; Is there a csh or csh like environment available?

Ksh sources can always be purchased from the AT&T Toolchest at about
$3000.00 a pop.  That's what we did a couple of years ago and have not
regretted it a bit.  It was well worth the investment by increasing
productivity.  Alas, you could wait till SysV 4.0 is released in which
case ksh will be the standard shell.


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Philip A. Gross			   |INTERNET:	pag%tcsc3b2 at wb3ffv.ampr.org
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