[Coco] GCC - Direct page and Double Float - Potential solution.

[John E. Malmberg]

KnudsenMJ at aol.com wrote:
> In a message dated 11/18/03 8:04:40 AM Eastern Standard Time, wb8tyw at qsl.net 
> writes:
> 
>>I need to find out what direct page locations that 
>> BASIC does not care about if they get trashed
> 
> I don't have a list handy, but this was common knowledge back in the glory 
> days -- lists of "safe" data locations were published in the Rainbow, passed 
> around on bull boards, etc.  The "Unravelled" books probably list them.  Make 
> sure you allow for Extended and Disk and Super-Extended (Coco3).

CB - DA, - Scratch
F3 - FF  - Unused

Now does anything else that would be resident with a C program, like an 
addon disk controller or DOS extender use these?

> BTW, ISTR that there is no advantage to putting arrays or strings in DP.

Arrays accessed sequentially are through index registers with auto 
increment/decrement, so they are slightly faster than a DP access. 
Random access in an array would be about the same as DP, assuming that 
you were able to keep the array index in a register.


Looking at the 68CH11, it looks like I can also set up targets for 
COCO2ROM, COCO3ROM, OS9, OS9II, FLEX09, and STANDALONE.  Of these, only 
COCO2ROM and COCO3ROM would need the "SOFT" register range restricted.

It does look like GCC will only use 31 registers, or for a COCO, 62 bytes.

-John
wb8tyw at qsl.net
Personal Opinion Only