Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!apple!dlyons
From: dlyons@Apple.COM (David Lyons)
Newsgroups: comp.sys.apple
Subject: Re: Hyper-C now fixed on an Apple IIgs.
Message-ID: <32170@apple.Apple.COM>
Date: 1 Jun 89 18:01:22 GMT
References: <21462@iuvax.cs.indiana.edu>
Distribution: usa
Organization: Apple Computer Inc, Cupertino, CA
Lines: 48

In article <21462@iuvax.cs.indiana.edu> beversdo@silver.bacs.indiana.edu (Tom Beversdorf    ) writes:
>I discovered the problem on the Hyper-C which wouldn't run on a IIgs
>computer because it intended to execute a "BRK" instruction.  The BRK
>on an Apple //e stays in the language card while an Apple IIgs switched
>into ROM memory.
>
>The Solution:
>
>    Go to the monitor on an Apple IIgs computer, type:
>
>        *E1/0010:5C D4 D0 00
> [...and a machien code patch that also involved changing the E1/10 vector...]

            AA    CCC  K  K  !
           A  A  C     K K   !
           AAAA  C     KK    !
           A  A  C     K K
           A  A   CCC  K  K  !

If there are *any* other interrupts (other than the BRK that Hyper-C executes
intentionally) occuring in your GS after making this patch, your system will
go south and you'll have to reboot.

$E10010 is the vector that all sorts of interrupts go through on the GS.  This
includes serial port interrupts, scanline interrupts, sound interrupts,
vertical blanking interrupts (for heartbeat tasks), mouse interrupts, quarter
second interrupts, ADB interrupts, desk manager interrupts (hitting Apple-Ctrl-
ESC), and others.

With the above patch, any of these interrupts will cause a jump to $00D054,
which contains Hyper-C code *if* you're lucky enough to have the right language
card bank switches in at the time the interrupt occurs.

Probably *no* interrupts occur typically when you're using Hyper-C.  Maybe it
even disables them--I don't know; I've never used it.  If you manage to do a
soft enough reboot from Hyper-C, your system will probably freeze mysteriously.

There's got to be a nicer way to fix Hyper-C.  (Like putting the entry point
to its BRK handler in main memory instead of the language card.)

 --Dave Lyons, Apple Computer, Inc.          |   DAL Systems
   AppleLink--Apple Edition: DAVE.LYONS      |   P.O. Box 875
   AppleLink--Personal Edition: Dave Lyons   |   Cupertino, CA 95015-0875
   GEnie: D.LYONS2 or DAVE.LYONS         CompuServe: 72177,3233
   Internet/BITNET:  dlyons@apple.com    UUCP:  ...!ames!apple!dlyons

   My opinions are my own, not Apple's.