Re: SCSI woes, again.

[dempson@actrix.gen.nz (David Empson)]

In article <326q15$667@eis.calstate.edu>,
Greg R. Achenbach <gachenb@eis.calstate.edu> wrote:
> This is the situation.  I'm trying to get a GS system put together for my 
> Grandfather.  I got a 40meg HD and a SCSI card and am having trouble 
> getting things to work.
> 
> Question #1 - How do you tell the difference between the different
> versions of the Apple II SCSI card (not HS).  I know I need rev.C for it 
> to work with GS/OS (at least I think I heard that somewhere) but don't 
> know how to tell the difference.  The big chip at the top of the card 
> that looks suspiciously like the ROM chip has a white sticker on it that 
> says "341-0437-A    Apple '87".

That is how you tell the difference - the three versions of the ROM
have different part numbers.  There are no other changes required on
the card.

The ROM part numbers are as follows:

Revision A:  341-0112A     (no copyright date shown)
Revision B:  341-0112B ?   (I haven't seen this one, so I'm not certain)
Revision C:  341-0437-A    (copyright 1987)

As you can see, you have revision C.  Revision C fixes several bugs,
standardises several SmartPort calls, adds support for the Apple CDSC
CD-ROM drive, and is the only version supported by GS/OS.

> Question #2 - There is a row of pins with a jumper block that I suspect 
> is for setting the SCSI ID of the computer/card.  The jumper is currently 
> on the pins closest to the center of the card.  Is this the correct 
> position for making the card ID #7?

Correct on both counts.  The jumper sets the ID number, with each pair
of pins corresponding to increasing ID from 0 to 7, starting at the
edge of the board.

> Question #3 - How do I determine if the drive is terminated and/or 
> supplying termination power?

I can't tell you how to find out if it is supplying terminator power -
this is a specific feature to each drive manufacturer.  There may be a
jumper to enable it.

You can usually identify a terminated drive by looking for a row of
three resistor packs (9 pin, single-in-line, value 220 ohms (I think)),
which are usually yellow or black, and are usually socketed.

> I tried it without an external terminator and with one.  Neither
> option worked.  If neither the card nor the drive are supplying term
> power, how do I get that power?

Enable the option on the drive to supply terminator power, if it has
one, or modify the card or drive to supply it.  I wouldn't recommend
supplying it from the computer, since the original Apple SCSI card
isn't terminated, and supplying terminator power may exceed the
supply rating of the IIe/IIgs 5 volt rail (SCSI termination may require
supplying up to 500 mA, which is the entire allocation of the slots).

> Is that what an "active terminator" does?

I don't think so.  An "active terminator" simply means that it is
implemented using an IC, rather than a resistor pack.  An active
terminator can selectively enable the termination via a control
signal.  The idea is that each device can have an active terminator,
and only the devices at the end of the chain have them enabled.  In
addition, the active terminator allows a device to be powered down
without interfering with the SCSI termination.  I don't see how an
external "active terminator" can work, unless the term has another
meaning, or some features are not available.

> The card  did work with another HD once when I tested it, so I think the 
> card is not defective, and the HD works on my other GS with a RamFast, so 
> it must be OK.  Anybody have words of wisdom for me?

The RamFast can supply terminator power, so this may be the reason for
the drive working with one card and not the other.
-- 
David Empson
dempson@actrix.gen.nz
Snail mail: P.O. Box 27-103, Wellington, New Zealand