Thread: 68k details
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Old 14 November 2018, 17:46   #778
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Originally Posted by roondar View Post
This is not correct AFAIK.

        Standard Instruction Execution Times
instruction    Size        op<ea>,An ^    op<ea>,Dn    op Dn,<M>
ADD          byte,word     8(1/0) +       4(1/0) +     8(1/1) +
              long         6(1/0) +**     6(1/0) +**   12(1/2)+

    + Add effective address calculation time
    ^ Word or long only
    * Indicates maximum value
    ** The base time of six clock periods is increased to eight        
       if the effective address mode is register direct or 
       immediate (effective address time should also be added)
This reads as 8 clocks for an add.l Dn,Dn command, unless I'm mistaken. I got this from:

The same figures can be found elsewhere as well. Strangely, the 'current' edition of the 68000 family programmers manual does not include cycle counts per instruction
I dont coded for long time, and checked my Amiga assembler book again, but add.l ea,Dn takes 6+ cycles, when ea for Dx is equal 0, then 6+0=6c.
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