Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.1 6/24/83; site oakhill.UUCP Path: utzoo!watmath!clyde!burl!ulysses!allegra!mit-eddie!godot!harvard!seismo!ut-sally!oakhill!davet From: davet@oakhill.UUCP (Dave Trissel) Newsgroups: net.micro.68k Subject: Re: 68010 replacing a 68000 Message-ID: <301@oakhill.UUCP> Date: Sat, 26-Jan-85 19:30:09 EST Article-I.D.: oakhill.301 Posted: Sat Jan 26 19:30:09 1985 Date-Received: Tue, 29-Jan-85 06:45:03 EST References: Reply-To: davet@oakhill.UUCP (Dave Trissel) Distribution: net Organization: Motorola Inc. Austin, Tx Lines: 31 In article <4909@fortune.UUCP> wall@fortune.UUCP (Jim Wall) writes: > > Can someone (or several someones) mail me the software aspects >of replacing a 68000 with a 68010? I know there are some stack >differences, are they always the same, is there more? The differences are: 1) All exceptions on the MC68010 have the generic vector word stacked before the Status Register and PC. The MC68000/MC68008 do not provide this vector word which identifies the exception type. 2) Both Bus exceptions and Address exceptions on the MC68000/008 stacked information AFTER the Status Register and PC concerning the bus fault. On the MC68010 these two exceptions stack the internal micromachine state which allows bus retry or simulation. The last items stacked are the Vector word, Status Register and PC just like all the other exceptions on the MC68010. 3) The MC68000/008 user instruction MOVE SR, was made privileged to allow for complete support for virtual machine systems. There are two ways to provide for compatibility here: A) change the user MOVE SR, code to use the new MC68010 instruction MOVE CCR, which has the same functionality but is not privileged. (It returns zeroes for the supervisor portion of the Status Register.) B) Include a small bit of code in the supervisor privileged exception handler to simluate the MOVE SR,. This is available from Motorola. The above should be the only differences encountered. Fortunately the MOVE SR in user code rarely occurs (although when it does it seems rampant) and the generic Vector word effects only code in some exception handlers. Motorola Semiconductors Dave Trissel Austin, Texas {ctvac,seismo,gatech,ihnp4}!ut-sally!oakhill!davet