[Coco] wanting to patch HPUT routine... (ping RG!)

[theother_bob]

----- Original Message ----
From: Robert Gault <robert.gault at worldnet.att.net>
To: CoCoList for Color Computer Enthusiasts <coco at maltedmedia.com>
Sent: Monday, August 17, 2009 5:18:58 PM
Subject: Re: [Coco] wanting to patch HPUT routine... (ping RG!)

theother_bob wrote:
> 

> 
> That makes sense. I did notice the testing routines to swap X or Y values if
> they were inverted. With Color Fog. I could overwrite that code, as I will
> already have done it, and possibly rewrite some of the optional methods that
> I'm not using. I'm sure that would be plenty of space for what I need to do... maybe enough to consolidate the other patch code.
> 
> Now I'm thinking about making a 512K only version with better speed and
> capability, and I'll probably drop Color from the moniker and go hi-res
> with it. With 512K in mind...
> 
> Is there any reason I couldn't copy the SECB ROM/RAM to a spare block,
> apply patches to the copy and then switch my patched block in to run FOG,
> then restore the unpatched (or less patched) block back upon exit? That
> would also benefit me by further reducing code overhead.

>You could encounter problems with that method. SECB switches MMU blocks whenever there is a need to access the Hi-Res text or graphics screens/buffers. Unless you alter the MMU block numbers used by SECB, you would find your personal MMU blocks get switched out of memory.

>Further, some programs may access the ROMs for routines because the programs over-write RAM memory to get more room. If that happened, again your patch might be switched out.

>You need to keep the above in mind if you expect Color Fog to be compatible with all third party programs.

> 
> What is the best (fastest?) way to copy one 8K block to another?
>
> Bob

>Since you don't require the presence of a 6309 CPU, the fastest method for transferring memory contents is to "stack-blast" from one MMU block to another.
By that I mean you set regS and regU to appropriate memory locations, pull D,X,Y from one stack and push D,X,Y onto the other stack.
Of course you must pre-save the original regS (and maybe regU) content and restore it after you are finished.
>



Thanks for the tips Robert and Darren. I don't really plan to change the MMU for running programs, but maybe to backup part of SECB. I have patches that I leave in place when exiting FOG (like 6ms step-rate, drive number layout, various common patches) and I have patches that I revert to original code for compatibility; mainly those that are designed specifically for the benefit of my gui, The mod you gave me for HPRINT and any mod to HGET/HPUT would be removed.

I understand SECB only makes use of the 128K memory map, regardless of  the presence 512K. I've figured out how to safely switch around the HPUT buffer block, so I can also safely use that kind of like a bunch of 8k ramdisks, but I mainly plan to store actual graphic data to be HPUT. I just had the idea of a modified HGET/HPUT routine that selects different "graphic pages" based on, say, high order bits of the Buffer number (always restoring the default page on exit.) hmmm.