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!cbosgd!ihnp4!houxm!vax135!cornell!uw-beaver!tektronix!decvax!genrad!panda!talcott!harvard!seismo!ut-sally!oakhill!davet From: davet@oakhill.UUCP (Dave Trissel) Newsgroups: net.micro.68k Subject: Re: 68010 replacing a 68000 Message-ID: <312@oakhill.UUCP> Date: Tue, 5-Feb-85 04:28:34 EST Article-I.D.: oakhill.312 Posted: Tue Feb 5 04:28:34 1985 Date-Received: Sat, 9-Feb-85 04:46:19 EST References: <301@oakhill.UUCP> Reply-To: davet@oakhill.UUCP (Dave Trissel) Distribution: net Organization: Motorola Inc. Austin, Tx Lines: 24 Summary: In article <87@drivax.UUCP> steve@drivax.UUCP (Steve Williams) writes: >> 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 ... >> B) Include a small bit of code in the supervisor privileged exception >> handler to simluate the MOVE SR,. This is available from >> Motorola. > >or C) Put a small bit of code in the supervisor privileged exception > handler to CHANGE the MOVE SR, to a MOVE CCR,. (Set > bit 9 (200H)). This takes 10 extra lines of code. > The only problem here is that it will not work for MOVE SRs in ROM. Actually, (B) above gives 3 methods using the exception routines: 1) identical to C) (which is obviously the fastest) 2) a routine which cleverly builds a MOVE CCR on the user's stack and passes control to it. (Note this will only work if the user is allowed to execute code in his/her data space.) and 3) a full MOVE SR simulation. (Works in all cases but quite ineffecient.) Motorola Secmiconductor Inc. Dave Trissel Austin, Texas {ihnp4,seismo,ctvax,gatech}!ut-sally!oakhill!davet