Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!uwm.edu!ux1.cso.uiuc.edu!ux1.cso.uiuc.edu!m.cs.uiuc.edu!kougiour
From: kougiour@m.cs.uiuc.edu
Newsgroups: comp.sys.mac.hypercard
Subject: Can XCMDs change the MMU mode?
Message-ID: <39800005@m.cs.uiuc.edu>
Date: 7 Nov 89 01:40:46 GMT
Lines: 16
Nf-ID: #N:m.cs.uiuc.edu:39800005:000:726
Nf-From: m.cs.uiuc.edu!kougiour    Nov  6 18:54:00 1989



I have written a very simple XCMD for the hypertalk. Its purpose
is to reset a card located in one of the Mac II slots. This
is done very simply by writting a zero into an address located
at the card's address space. The routne is written in MPW C 3.0.
Since I cannot access this address when the MAC II operates in 24 bits
mode I SwapMMUMode() to 32 bits before the operation and then back to 24 bits.

 The routine
works ok as a seperate application but when I used it as an XCMD the
hypercard crashes: "Hypercard quits unexpectedtly (28)". By
commenting part of the code I discovered that the crash happens
somewhwere around the first SwapMMUMode call.

Does anybody has an idea what happens and how I can recover? Thanks