UNIX pc 2nd drive modifications

[Gil Kloepfer Jr.]

In article <9056 at chinet.chi.il.us> ignatz at chinet.chi.il.us (Dave Ihnat) writes:
>As there are many out there in my situation, and I'm getting this question
>often, let me see if I'm sure I've got this correct:

not really...

>1)  The ICUS mod will require removal of the PAL, and modification and/or
>    addition to the jumper wires installed on the motherboard for the P5.1
>    upgrade.  Some of these wires, however, are usable as-is.

This is true...  It will require removal of the PAL, insertion of some more
jumpers, and removal of some inter-pin jumpers on the socket.  All of the
jumpers from the socket to various locations on the motherboard are usable
as-is.  However, this is not noted in the instructions...I realize this
and apologize for not mentioning it.

>2)  The Milton mod will only require removal of the PAL, and insertion of
>    a daughter board.

This is incorrect.  The Milton mod will require the same additions of
jumpers as the ICUS mod.  John did a smart thing and avoided the removal
of some jumpers on the socket.  This, however, doesn't give you a significant
advantage over the former.  If you add the extra jumper wires, your original
P5.1 upgrade PAL will more then likely not function with the extra jumpers,
and moreover the machine will likely not work.  A simple DIP header jumping
the data separator in to the first drive buffer out in either upgrade will
facilitate bypassing the mod if you goof-up somewhere in the installation.

>In this case, then, is it safe to assume that the Milton modification is the
>simplest for those who've already done the P5.1 upgrade?

The only advantages to using the Milton modification over the ICUS mod are
that you don't need to wire a circuit on perfboard and that you have a
provision for 2 more drives should the OS support it in the future.  Otherwise
they are not different.

The advantage of the ICUS mod is that the chips used in the upgrade are
common and do not need any programming of any kind.

Being that I was the one who did the design and writing of the ICUS mod, I
can say I know what is involved in the ICUS mod.  Since John is doing his
mod the same way, with a few differences in circuit design, I can also
say that you really don't go wrong with EITHER upgrade.  HOWEVER-- either
upgrade assumes that you really feel comfortable and have experience
soldering and identifying certain electrical components.

I remember posting an article a while ago listing the comparisons between
the two mods, and I said pretty much the same thing then.  I personally
recommend that you pick-up the Milton mod if you have any problem constructing
a small circuit on perfboard or desire the capability for 4 drives.  In
the same breath, however, I say that the small circuit needed in the ICUS
mod requires only a little more skill than that required to do the rest
of the mod.  Certainly, if you plan on upgrading more then one or two
machines, I highly recommend the Milton mod!

If anyone else has any questions regarding either of the upgrades, I
would recommend that you write to me or John Milton and we'd be happy
to answer any questions you have.

Gil.
-------
| Gil Kloepfer, Jr.
| ICUS Software Systems/Bowne Management Systems (depending on where I am)
| ...icus!limbic!gil   or    gil at icus.islp.ny.us