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Old 22 August 2015, 20:09   #242
68k wisdom
meynaf's Avatar
Join Date: Nov 2007
Location: Lyon (France)
Age: 43
Posts: 1,935
Originally Posted by Megol View Post
Yes it is easy. The only complication is the sign extension but that is required elsewhere.
So Gunnar's excuses for rejecting my MOVEM.B idea were invalid
(and the removal of MOVEM.W in the coldfire doesn't look very smart either)

Originally Posted by Megol View Post
DIV doesn't touch any critical part of the pipeline so that isn't a problem. In my design it was actually handled a lot like a load missing the cache, this means there is no extra hardware needed for the variable latency operation and starting the execution would be a "store-data" operation in the integer unit.
If DIV is no big deal, would an integer SQR be a problem ?

Originally Posted by Megol View Post
I never started implementing LINK.
Too bad. Why did you stop doing your 68k implementation, btw ?

Originally Posted by Megol View Post
If one have proper microcode support MOVEP isn't hard to execute without extra hardware but it would be slow. Unlike x86 the 68k doesn't really need full microcode support and adding it complicates a critical part - the decoder.
Other 68k instructions need microcode as well. Oh, wait. They're the 020+ insns everyone removes too
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