Xref: utzoo comp.binaries.ibm.pc.d:672 comp.sys.ibm.pc:17955
Path: utzoo!utgpu!water!watmath!clyde!bellcore!rutgers!ukma!husc6!bbn!humming!simcha
From: simcha@humming.UUCP (Simcha Lerner)
Newsgroups: comp.binaries.ibm.pc.d,comp.sys.ibm.pc
Subject: Re: EXEPACK (was Re: Error in MSKERMIT 2.31 posting)
Message-ID: <244@humming.UUCP>
Date: 10 Aug 88 02:58:30 GMT
References: <8159@watdragon.waterloo.edu> <830@naucse.UUCP>
Reply-To: simcha@humming.UUCP (Simcha Lerner)
Organization: Kurzweil A.I. Waltham, Mass.
Lines: 43

In article <830@naucse.UUCP> wew@naucse.UUCP (Bill Wilson) writes:
>Exepack is a program that is supplied with all of the languages
>that I have seen from Microsoft.  It is a compression utility
>that deletes sequences of identical characters from an executable 
>file.  It also optimizes the relocation table that can also make
>execution time faster. 
>-- 
>Bill Wilson                          (Bitnet: ucc2wew@nauvm)
>Northern AZ Univ
>Flagstaff, AZ 86011
>{These views are mine and do not necessarily reflect those of my employer}


Sorry,  but  there  is  nothing  that will make your program execute faster
except compiling with a better compiler or running on a faster computer.

The main saving of exepack is to save _disk_space_ by making the disk image
smaller.  As  mentioned  before,  this  is  done by compressing out runs of
uninitiated data space and the like.

There  is  controversy  on whether this speeds up load time or not. EXEPACK
inserts  a  unpacker  that  becomes  the  entry  point of the program. This
unpacking  process  takes a finite amount of time that otherwise would not
take  place  in  an  unpacked version of the program. The ratio of the time
saved  from  loading  a  smaller  file vs. unpacking to original offsets is
quite variable from my experience.

By  the  way  -  some versions of exepack (maybe all?) seem to count on the
8086  1MB  memory  wrap-around  behaviour  (which  is  emulated on AT class
machines  by  gating the A20 line in real mode) for unpacking, and complain
loudly  (about  a "corrupted packed file") if the wrap-around is not taking
place.

In my opinion, don't bother with exepack unless you really need to save the
disk space (eg: it's going onto a floppy).


Simcha Lerner

...harvard!humming!simcha

All opinions are my own...although you are welcome to share them.