executor/docs/MacHack_96.rtf

{\rtf1\mac\deff2 {\fonttbl{\f0\fswiss Chicago;}{\f2\froman New York;}{\f3\fswiss Geneva;}{\f4\fmodern Monaco;}{\f16\fnil Palatino;}{\f20\froman Times;}{\f21\fswiss Helvetica;}{\f22\fmodern Courier;}{\f23\ftech Symbol;}}{\colortbl\red0\green0\blue0;
\red0\green0\blue255;\red0\green255\blue255;\red0\green255\blue0;\red255\green0\blue255;\red255\green0\blue0;\red255\green255\blue0;\red255\green255\blue255;}{\stylesheet{\s243\tqc\tx4320\tqr\tx8640 \f16\fs20 \sbasedon0\snext243 footer;}{\s245 
\f16\fs18\up6 \sbasedon0\snext0 footnote reference;}{\s246 \f16\fs20 \sbasedon0\snext246 footnote text;}{\s250\li720 \f16\fs20\ul \sbasedon0\snext0 heading 6;}{\s251\li720 \b\f16\fs20 \sbasedon0\snext0 heading 5;}{\s252\li360 \f16\ul \sbasedon0\snext0 
heading 4;}{\s253\li360\sb120 \b\f16 \sbasedon0\snext0 heading 3;}{\s254\sb120 \b\f21 \sbasedon0\snext0 heading 2;}{\s255\sb240 \b\f21\ul \sbasedon0\snext0 heading 1;}{\f16\fs20 \sbasedon222\snext0 Normal;}}{\info{\title Executor Internals}{\subject 
How to efficiently run Mac Programs on PCs}{\author ctm + mat}}\margl720\margr720\margt-1440\margb-1440\gutter1080\widowctrl\ftnbj\fracwidth\margmirror \sectd \sbknone\linemod0\linex0\cols1\endnhere {\footer \pard\plain \s243\tx4320\tqr\tx8640 \f16\fs20 
\tab Executor Internals\tab \chpgn \par 
}\pard\plain \qc \f16\fs20 {\fs36 Executor Internals:\par 
How to Efficiently Run Mac Programs on PCs\par 
\par 
}{\plain \f16 Mathew J. Hostetter }{\plain \f22 <mat@ardi.com>}{\plain \f16 \par 
Clifford T. Matthews }{\plain \f22 <ctm@ardi.com>\par 
}{\fs18 After MacHack '96, this paper will be available from}{\f22\fs18  http://www.ardi.com}{\fs18 \par 
}{\plain \f16 \par 
}\pard Executor is a commercial Macintosh emulator that uses no software from Apple, but is still able to run much 680x0 based Macintosh software faster on Pentiums than the same software runs on 680x0
 based Macs.  This paper contains some implementation details, including descriptions of Executor's synthetic CPU, graphics subsystem and debugging environment.  Portability issues, current limitations and future plans are also presented.{\fs36 \par 
}\sect \sectd \sbknone\linemod0\linex0\cols2\endnhere \pard\plain \s255\sb240 \b\f21\ul Executor Overview\par 
\pard\plain \s254\sb120 \b\f21 What Executor is\par 
\pard\plain \f16\fs20 Executor is a commercial emulator that allows PCs to run many Macintosh applications.  Executor does not require Macintosh ROMs or a Macintosh System file and contains no Appple code it
self.  Executor was written entiredly by engineers without Macintosh backgrounds who have not disassembled any of Apple's ROMs or System file.\par 
\pard\plain \s254\sb120 \b\f21 Limitations\par 
\pard\plain \f16\fs20 
Because Executor was written strictly from publicly available documentation (Inside Macintosh, Tech. Notes, etc.), programs which make use of undocumented features of MacOS may fail under Executor.  Furthermore,  there are some portions of MacOS that we ha
ven't implemented yet.  Executor is sufficiently large that there are probably bugs in some of o
ur code as well.  We realize these are major limitations, but this paper is primarily concerned with implementation details that are interesting to our fellow programmers as opposed to feature sets and limitations which are of more concern to end users and
 our marketing department.\par 
\pard\plain \s255\sb240 \b\f21\ul Design Goals\par 
\pard\plain \f16\fs20 Our goal is for Executor to be accurate, fast and portable.  Beyond that, completeness is a secondary issue.\par 
\par 
Accuracy means that each subsystem that we implement should behave exactly according to the functional specs for the subsystem that we've derived from a combination of reading documentation, writing test cases and running programs under Executor.\par 
\par 

Fast is harder to qualify.  As programmers we like to use advanced techniques that will result in programs running under Executor as quickly as possible.  Unfortunately, we have a limited number of engineer hours in a week and most engineering time is spen
t implementing new subsystem