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Conference hydra::amiga_v1

Title:	AMIGA NOTES
Notice:	Join us in the NEW conference - HYDRA::AMIGA_V2
Moderator:	HYDRA::MOORE

Created:	Sat Apr 26 1986
Last Modified:	Wed Feb 05 1992
Last Successful Update:	Fri Jun 06 1997
Number of topics:	5378
Total number of notes:	38326

1328.0. "68010 question" by UTROP1::TRAMONTINA () Wed Apr 13 1988 08:50

    Hi,
    
    I am an Atari ST owner who's confused by the fact that on the Amiga
    everybody has an 68010 installed and in the Atari world 'nobody'
    has. OK on the Atari the 68000 is soldered on the board, on the
    Amiga it's in an socket (I think).
    
    The other problem is the instruction(s) that are perfectly legal
    on an 68000 in user mode. But will cause problems on an 68010, 68020
    (execption, Privileged Instruction (???)). On the Amiga there's
    a public domain program to handle the exception in such a way the
    program gets the wanted results (the statusregister I beleive) and
    the machine doesn't crash (or as we (Atarians) say "Bombe out").
    
    What I want to ask is:
    
    -	Does somebody have the source code of that program, if so will
    you send me a copy?
    
    -	If no source available how is it done?
    Just execute the same instruction in the traphandler because that's
    always in supervisor mode. And pass over the results?
    
    I anybody could help me I would be very pleased.
    
    Renato.
    
    (UTROP1::TRAMONTINA)

T.R	Title	User	Personal Name	Date	Lines
1328.1		WJG::GUINEAU		`Wed Apr 13 1988 09:24`	12
	I can't remember exactly the differences, but I think if the ST operating system doesn't expect a 68010 there, you'll have more than just your own programs to deal with... I think on the 68010, the "get processor status" instruction is now privleged so executing it in other than super mode causes an exception. I think there was also some additional info added to the interrupt stack frame or something like that?? John
1328.2		STAR::BANKS	In Search of Mediocrity	`Wed Apr 13 1988 10:02`	5
	I think the biggest problem is the difference in the exception and/or trap stack frames. The 68010 pushes an extra word, and since the program is just expected to know this stuff when it unwinds the stack, you'd better know which processor you're running on beforehand or you might not unwind the right amount.
1328.3	seen that hack..	MTBLUE::PFISTER_ROB	Steak knife, puta hole in my head	`Wed Apr 13 1988 10:56`	6
	The guilty instruction is a MOVESR which is well documented in ALL of the Amiga RKM books as a no-no. Fred Fish wrote a hack that caught the invalid instruction processor trap, and either simulated it, or did it in `supervisor' mode. I'll see if I can't dig up what exactly he did... Robb
1328.4		BAGELS::BRANNON	Dave Brannon	`Wed Apr 13 1988 13:38`	21
	re: .0 "on the Amiga everybody has an 68010 installed" Why? Psygnosis in the UK is famous for copy protected games that won't run on a 68010. I seem to remember AmigaBasic also has problems with it. Decigel and the 1.2 enhancements to the OS, will let you run stuff on the 68010, but I believe the performance boost is only 5-10%. Depends on if the stuff you're doing is uses the 68000 a lot. The performance boost on the ST might be greater, on the Amiga a lot of stuff is off-loaded to custom chips instead of the 68000. The ST's version of GEM appears to be the main reason why the 68010 won't run. I saw mention on usenet of some German folks that had "fixed" GEM so that it can run on 68010 and 68020. Atari hasn't done that yet. GEM is basically doing the bad things that Motorola says don't do if you want to be compatible with the 68xxx family. Both in the use of address fields and stack manipulation. -dave
1328.5		LEDS::ACCIARDI		`Wed Apr 13 1988 14:26`	11
	AmigaBASIC runs fine with the 68010. You might be referring to it's 24 bit address limitations, which would prevent it from running from 32 bit ram on an '020. Apparently plenty of people have yelled at Psygnosis about their '010 and '020 incompatibilities. Their latest ad in AmigaWorld makes special mention that '... runs on Amigas with 68000, 68010, and 68020 uprocessors...' Ed.
1328.6		TRCT02::PINTER	atomicus et citerox	`Wed Apr 13 1988 16:50`	5
	Um. Yeah, the MOVESR was replaced in 1.2 with a call to a supervisor mode routine which plucked the condition codes correctly. All recent programs use this routine (called GETCC?, I forget) rather than the MOVESR. DECIgel isn't required anymore either...