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Topic       : Chips 'n Chips
Author      : Michael Ruge
Version     : chips_x.hyp (01/05/2001)
Subject     : Dokumentation/Hardware
Nodes       : 1505
Index Size  : 35662
HCP-Version : 3
Compiled on : Atari
@charset    : atarist
@lang       : 
@default    : 
@help       : 
@options    : -i -s +zz -t4
@width      : 75
View Ref-File

   Modifying of the Atari hostadaptors in the MegaSTE and the STACY
      (Copyright 01-05-1995 Michael Ruge - 65428 Rüsselsheim)
    (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 harddiscdriver!).

   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 hard-
   disc 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 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 inscription 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 com-
   puter 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 documentation).

   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 cablelengths 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 (particu-
   larly 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 centime-
   tres/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!).

     Kapitel Der Hostadapter im MegaSTE und der STACY, Seite 4