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From: dpi@loft386.uucp (Doug Ingraham)
Newsgroups: comp.os.minix
Subject: Re: PC Minix Memory Models (Was (none))
Summary: Small or Tiny models, Projects, Questions, and Rambling
Message-ID: <1990Jun12.053051.28862@loft386.uucp>
Date: 12 Jun 90 05:30:51 GMT
References: <21641@nigel.udel.EDU>
Organization: Lofty Pursuits Public Access Unix for Rapid City, SD USA
Lines: 35

In article <21641@nigel.udel.EDU>, V2057A%TEMPLEVM.BITNET@cornellc.cit.cornell.edu (Juan Jose Noyles) writes:
> 
> I'm a little confused here.  Does the compiler determine the MINIX memory
> model, or is it something else?  If it is the compiler, does this mean that
> I could recompile in under Turbo-C, for example, using its ability to choose
> different models?  If not, how can I select a different model?

The Minix C compiler system can generate either combined I&D (Instruction &
Data) or separate I&D load files.  The operating system knows about both
kinds of load files.  If you generated a Huge, Large, Medium, or Compact
model program you would have to modify Minix to understand about these very
strange looking things.  Modifying the OS to support the other models wouldn't
seem to be that difficult.  But without a native compiler that could generate
those formats you would be spending all your time cross compiling, cross
assembling, cross linking.  It would also be slower to execute and having
programs that large would prevent you from multitasking because only 1
could fit in 640k with the OS + Ramdisk.

What bothers people most about the 64K I & 64K D space limitation?  Is
it the 64K Instruction or the 64K Data?  If it is the instruction limit
that is less of a problem.  We could implement a form of Shared Library
where all the library routines that are used by the Kernel+MM+FS and any
other routines used by the vast majority of the commands would be in its
own 64k space.  I call this a Global Shared Library.  If it is the 64K
Data as I suspect then there is no good easy solution.

In addition to the idea of the Global Shared Library I would like to
see shared Text.  Perhaps someone might assign this as a class project
next Fall so that it could get into version 2.  Both of these things
would benefit users of other CPU's as well.

-- 
Doug Ingraham (SysAdmin)
Lofty Pursuits (Public Access for Rapid City SD USA)
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