[Coco] Is the 6809 is flawed?

Dave Philipsen dave at davebiz.com
Fri Sep 7 14:44:38 EDT 2018

If you haven’t watched episode 73 of CoCoTALK!, you should. A contention is brought up that claims the 6809 ASL instruction “does not work for signed math”.  Is it true?  After 40 years are we just now finding out that the 6809 has a bug and that Motorola engineers “messed up here”?  John Linville was the first to notice the flawed tutorial and comment about it here: https://retrotinker.blogspot.com/2018/09/yes-lsl-and-asl-really-are-same.html

You can see for yourself by visiting the CoCoTALK! Webpage here: http://cocotalk.live/video-episodes/ and viewing episode 73.  You’ll find the interesting part around 1:23:00.  Hear for yourself and determine whether our favorite CoCo processor, the 6809 is flawed and in regard to the Arithmetic Shift Left if you should “just never use that in life...never use that command and you’ll be fine.”


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