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PostPosted: Sun Feb 17, 2013 7:40 pm 
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Joined: Sun Feb 17, 2013 7:16 pm
Posts: 10
Hi,

i have a few problems understanding which value the pc contains at any given time of execution.

Is the program counter incremented directly before or after a prefetch (instruction or extension word) ?

I am wondering because of instructions like dbcc. In the manual it says the pc contains the address of the instruction + 2 at the time when generating the new pc for branch.

Because of the prefetch cycle of the last instruction, the pc seems to increase directly before a prefetch. If so it means the first instruction after a reset doesn't increase the pc.


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PostPosted: Mon Feb 18, 2013 7:34 pm 
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Joined: Mon Jul 26, 2010 11:43 pm
Posts: 198
Location: Aurora, IL
After the micro/nano-code consumes the word?

By the time the PC addition portion of the pipeline executes the PC has advanced past the opcode word, ready to fetch the branch target word.


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PostPosted: Mon Feb 18, 2013 9:00 pm 
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Joined: Sun Feb 17, 2013 7:16 pm
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I got information, that incrementing pc is handled in microcode and not hardwired to prefetch.


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