Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!cs.utexas.edu!oakhill!paco
From: paco@oakhill.UUCP (Paco)
Newsgroups: comp.sys.mac.programmer
Subject: Re: LSC & SE/30
Summary: M68020, M68030 instruction set differences
Message-ID: <1875@devsys.oakhill.UUCP>
Date: 24 Feb 89 16:29:02 GMT
References: <1524@murdu.OZ> <1253@husc6.harvard.edu>
Organization: Motorola, Austin, TX
Lines: 52

In article <1253@husc6.harvard.edu>, siegel@endor.harvard.edu (Rich Siegel) writes:
> In article <1524@murdu.OZ> grae@murdu.OZ (Graeme Gerrard) writes:
> >Anybody know whether there is a version of THINK C
> >around that uses the 68030/68882 of IIx and SE/30.
> >Is there one planned, any idea when it's due?
> 
> 	The current version of LightspeedC generates code for the 68020
> (long multiply/divide, bitfields), which is upward-compatible with the 68030,
> and for the 68881, which identical in object format to the 68882.
> 
> 	LightspeedC currently doesn't support the PMMU instructions on the
> 68030, but a future version may support it in the inline assembler.
> 
> 	[Note that the ONLY software difference between the 68020 and the 68030
> is the set of PMMU instructions.]
> 
> 		--Rich
> 
> Rich Siegel
> Staff Software Developer
> THINK Technologies Division, Symantec Corp.


Actually, there's more to the software differences than just PMMU instructions.
The MC68030 implements a subset of the MC68851 PMMU functionality and drops a 
couple other opcodes out of the MC68020 instruction set:

	CALLM	Save current module state on stack; Load new module state
		from destination
	RTM	Reload saved module state from stack
	
The data cache on the 030 might also change the way a bus trace looks...
All totaled, people writting in LSC (yours truly included) won't feel these 
differences.

    paco.

---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- | ---- 

Macintosh Software Developer
Motorola Microprocessor Division
Austin, Texas

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