[Coco] The Definitive Post on the CC-Five ;)

[Jeff Teunissen]

jdaggett at gate.net wrote:

[snip]

> Any expansion of the CPU would be to drop the DAT and expand the Program co 
> unter to 24 bits. That would yield a direct addressing capability of 16M. That 
> would put it on par with the TC70 and MM1. Alternatively a "CALL" and 
> "RETURN" instruction would need to be added to the assembler. I believe that 
> would not be to difficult to implement. The assembler would have to determine if 
> the address jump were out of the range of the current 64K block and addjust the 
> upper byte of the PCR to reflect which block of 64K the call would be. In the CPU 
> the PCR could be stacked internally with the CALL instruction and pulled back off 
> with the RETURN instruction.

Even with segmented addressing you still want DAT for Level 2 [Nitr]OS-9,
otherwise you would have to switch segments to use every system call. Besides,
address mapping is the first step toward virtual memory paging which is doubly
cool (and ironically allows you to use much less memory).

-- 
| Jeff Teunissen -=- Pres., Dusk To Dawn Computing -=- deek at d2dc.net
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