[Coco] Is the 6809 is flawed?

Salvador Garcia salvadorgarciav at yahoo.com
Fri Sep 7 16:29:00 EDT 2018

 I am not familiar with 6809 assembler, but for this bug to have gotten past Motorola testing is, as Vizzini would say, Inconceivable!


    On Friday, September 7, 2018, 1:47:13 PM CDT, Dave Philipsen <dave at davebiz.com> wrote:  
 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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