UNIX-pc Second Hard Drive - Information (lengthy)

[Gil Kloepfer Jr.]

My apologies to those who have seen this before, or who may be otherwise
"offended" by the repost of this article -- I have been swamped with
questions about the second hard disk upgrade, and I see no need to send
out individual mail to each person.  Here's the poop:

Question:  What's the difference between the P5.1 upgrade and the second
           hard disk expansion upgrade?

Answer:

P5.1 is a REVISION DESIGNATION of the motherboard.  The original P5.1 field
upgrade was an unreleased AT&T field upgrade which added a PAL and a bunch
of jumpers on the motherboard and "turned-on" some OS features, and decoded
a 4th head select line from an internal port called MCR2.

The second hard disk expansion is a SUPERSET of the P5.1 expansion.  The
second hard disk upgrade upgrades a motherboard to P5.1 (has to, P5.1 is
just a motherboard which has MCR2), decodes the 4th head select from MCR2,
and decodes another bit on MCR2 which allows a second disk drive select.

Question:  Do I need to install the second disk upgrade in order to have
           the P5.1 upgrade?

Answer:

No, but it is kind of silly to do P5.1 without doing the 2nd disk upgrade
unless you only plan to install a bigger drive in your 3B1.  There is
somewhat more wiring involved in the construction of the 2nd disk upgrade,
but it shouldn't be scary if you feel comfortable running jumpers all around
on your motherboard.

P5.1 alone doesn't really add any new functionality to a 3B1 with a stock 
40 or 67 meg hard disk drive.  Neither does the second hard disk expansion
unless you add the second hard disk.

Question:  I already did the original PAL-based P5.1 motherboard upgrade.
           Does the second hard disk expansion mean undoing all my work?

Answer:

No.  If you socketed the PAL in the P5.1 upgrade, you need only add 7 more
motherboard jumpers, one modification to the motherboard, and construct
the expansion board.  The socket on the motherboard where you had the PAL
will be used to connect the expansion board to the motherboard via a
ribbon cable (there will be a 20 pin DIP header on the motherboard side
of the ribbon cable which now plugs into the motherboard).

One other note is that the ICUS second disk expansion requires no PAL
programming to be performed.  The only chips used are standard LS TTL
chips and two hard disk buffer ICs (available at outfits like Jameco
Electronics in California and some local electronics supply houses).

Question:  What's the difference between the ICUS second hard disk upgrade
           and the one that John Milton is working on?

Answer:

John is planning on eliminating one phase of construction of the second
disk upgrade by distributing a completed PC board with his upgrade
instructions.  The PC board will eliminate the need to wire a small 5-chip
circuit on a perfboard (the perfboard-wired circuit is fairly simple and
straightforward, but might look scary to some folks).  John's upgrade
will also provide the capability for 4 hard disks *when the software to
use them comes available*.  Currently, the OS software only allows 2
hard disks to be connected, and 4 partitions to be simultaneously mounted.

Both the ICUS upgrade and John's upgrade will require the motherboard to
be modified and jumpers installed.  This requires a significant amount
of patience and care to be performed correctly.

Question:  Is any additional software required for the use of two
           disk drives?

Answer:

No, this is built-into the operating system.  The devices for the second
hard disk are /dev/rfp010 - /dev/rfp01f  and /dev/fp010 - /dev/fp01f .

Question:  I am interested in getting the ICUS upgrade?  How do I do so?

Answer:

The ICUS upgrade is a manual, not a kit.  It provides the items outlined
below:

	1.  Schematic diagram of the upgrade (extension) board
	2.  Full instructions regarding the motherboard
	    modifications and assembly of the extension board
	3.  Theory of operation of the modification
	4.  Photographs (aproximately 10) showing the more
	    difficult portions of the upgrade (sections of the
	    motherboard where wires were routed, socket installed,
	    a section where wires are soldered to pads instead of
	    chips, construction of the extension board)
	5.  Diagrams (where the photos fall short) and construction
	    hints

For an additional fee of $5, we will also send a disk with the extended
diagnostic on it (this contains commands which allow larger disks to
be formatted [ie. disks with more than 1024 cylinders] and tested, and
it also allows you to partition your disk into multiple smaller partitions).

To order the upgrade plans, send a check (or money order) for the correct
amount:

	$30 - Hard disk upgrade plans
	$35 - Hard disk upgrade plans with diagnostic disk

...and NET ADDRESS to:

		ICUS Software Systems
		Hard disk expansion plans
		c/o Lenny Tropiano
		P. O. Box 1
		Islip Terrace, NY  11752

Make checks payable to Lenny Tropiano or Gil Kloepfer.

We are requesting that you send us your net address so that we can send
you e-mail when we send out your plans, and so that if any problems are
discovered after we mail your plans, that we can contact you in the
future.

If you are not confortable following a schematic diagram and constructing
a small circuit on perfboard, we recommend that you wait for John Milton's
upgrade since the assembled PC board will eliminate this step.  I don't
know when John's upgrade will be available.  Remember that for both upgrades
the motherboard modifications will still be required.

I hope this answers some of the questions I have been receiving.

-------
Gil Kloepfer, Jr.          U-Net: {decuac,boulder,talcott,sbcs}!icus!limbic!gil
ICUS Software Systems      Voice: (516) 968-6860 [H]   (516) 746-2350 x219 [W]
P.O. Box 1                 Internet:  gil at icus.islp.ny.us
Islip Terrace, NY  11752   "Life's a ...  well, you know..."