[Coco] CoCo 3 MMU test for all

[Darren A.]

> 
> With an 0,X assembler directive most assemblers will opt to a 5 bt offset with the offset 
> value being zero. This is the same instrruction as ,X with the exception that the 6809 takes 
> one more machine cycle to execute an LDB 0,X than that of LDB ,X. 
> 

Same operation, different object code.


> 
> The issue is the read from the GIME chip has no bit 6 an d 7 from the MMU registers. 
> Therefore unless the actual iternal workings of the GIME chip are known, these bit may or 
> maynot be tristated. The buss is left floating. The common read in Basic is $78. No other. 
> This tends to lead me that it is not noise.
> 

It may very well not be noise. The common read, as you say, is coming from the PEEK command. Robert G. has confirmed that a different result can be obatined using assembly instructions. The question remains as to whether or not the value of the instruction bytes are playing any role in this matter.

Darren


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