(Copyright 01-05-1995 Michael Ruge - 65428 R|sselsheim)
(Translation 07-10-1995 Frank Szymanski - 45889 Gelsenkirchen)
The hostadaptor in the MegaSTE and STACY is only able to use
one harddisc with unit number SCSI 0 without parity. With this
little modification the hostadaptor (fully Atari-compatible) is
able to adress two harddiscs (compatible to the Megafile 44
hostadaptor, which means that you can use the regular harddisc
driver!).
All you have to do is to add two wires and a 1 KOhm resistor !
The one wire goes from chip U4 pin 12 to chip U8 pin 1, the other
from chip U8 pin 2 to pin 44 of the seconds (the new one !)
harddisc SCSI cable.
Both harddiscs are connected to the same SCSI cable (therefore
you have to squeeze a second 50 pin liner onto it) and the second
harddisc has to be jumpered onto SCSI ID 0 (yes, you are right:
both harddiscs have ID 0!). Cut the SCSI-cable between the first
and the second harddisc, only and exclusive at pin 44 (directly
behind the 50 pin wide socket of the first harddisc is highly
recommended). Now the second wire from chip U8 pin 2 has to be
soldered at this vein (to the vein which goes to harddisc no. 2) !
After you have done this, solder the 1 kiloohm resistor from
pin 1 of the resistorarray RP3 (pin 1 is the one which points to
the description REV. 2 or REV. 3) to pin 2 of chip U8.
Now you need a Y-cable for the harddiscs voltage and to put
the computer into operation with the two harddiscs. If necessary
you must reconfigure your harddiscdriver so it can find the new
harddisc on system-bootup (Please refer to the drivers'doc).
Beware : The hostadaptor has only been built for short SCSI
cables ! The cable should never (!!!) be any longer than 20
centimetres/7.8 Inch. For larger cable lengths there is another
termination used than the hostadaptor has (impossible to change!).
On the other hand, you only need short cablelengths in the
MegaSTE and the STACY (particularly in the STACY there is only
room for one harddisc when you also want to use the discdrive) and
even when you use a caddy 20 centimetres/7.8 Inch are more than
enough !!!!! Furtheron NONE of the harddiscs is allowed to be
terminated, so * FUNDAMENTALLY * remove the ending terminators
otherwise the drivers on the hostadaptor were overloaded and may
disappear in a cloud of smoke (no joke !).
In the end: The device adresses:
dip 1 dip 2 dip 3 --------- dip-switches on the hostadaptor
on on on only ACSI-unit 0 (Atari default)
off on on ACSI-unit 0 for the old harddisc
ACSI-unit 1 for the new harddisc
off off on ACSI-unit 1 for the old harddisc
ACSI-unit 2 for the new harddisc
off on off ACSI-unit 2 for the old harddisc
ACSI-unit 3 for the new harddisc
off off off ACSI-unit 3 for the old harddisc
ACSI-unit 4 for the new harddisc
LIABILITY
I, Michael Ruge, (me, Frank Szymanski, too) cannot accept ANY
liability for direct or indirect damage in financial, material or
any other way which are caused by the use of these instructions.
These instructions were produced and tested with the highest care.
I cannot estimate how this list, instructions or modifying of
your computer corresponds to your abilities. The person who
carries out the above-mentioned modifications always bears full
responsibility. In case of doubt let a friend or even your
computer dealer do the modifications. I cannot take responsibility
for irregular done works (e.g. computer is out of order) because I
cannot verify if your abilities corresponds to the demands to do
the modifications in a correct way.
This is especially when you work with voltage or currents.
Electrotechnical laymen have to * STAY AWAY * from voltages higher
than direct voltage 120 volts or alternating voltage 50 volts (in
Germany!). In other County's/Country's take a look at the law of
order for electrical units and regulations.
Electrotechnical laymen are all persons, who did not get
equivalent instructions or who do not have an electrotechnical
education.
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