[Coco] Patching NitrOS9 for 8 meg

[Dave Philipsen]

That’s interesting.  So there are 32 task registers in the MMU of the CoCoMem, right?  Are they extended out from the original two at $FFA0-FFAF? How do the new registers map into the I/O space?

Dave

> On May 3, 2018, at 11:17 AM, L. Curtis Boyle <curtisboyle at sasktel.net> wrote:
> 
> We did briefly. It does run the system slower (because it has to swap MMU blocks in/out in the system map every time you went between SCF and RBF based system calls - reads, writes, getstats, setstats, etc.), and we needed to keep our printers running as fast as possible, so we went back to straight level 2. It did give us (effectively) an 80K system map.
> Now, Jim Brains CocoMem is adding to the Task register - instead of being just 0 and 1 to choose from, he is bumping it up to 0-31 (and that is the maximum processes allowed under Coco Level II, anyways… and one would likely run out of system RAM before that happens). With the main system map being task 0, and Grfdrv/user processes being tasks 1 and up, the system has to manually change the MMU registers for every time you switch to a non-main system task. With Jim’s solution, this can be eliminated, and just change the single task register instead (you would update the MMU mappings whenever they need changing, thus maintaining compatibility with utility programs etc. that manually read those in - like MDIR, DMEM, etc. for example).
> This will speed up multi-tasking, and the one could reserve 3 (instead of 2) tasks for the system - system/SCF, system/RBF, and Grfdrv - for faster task switching, alleviating the slowdown we encountered with Level III. Level III still needs patching to work with the current NitrOS9, however - I believe it was designed to for the “single driver” model for each device, not split apart into sub-modules (like RBSuper, then Cocosdc, or IDE, etc.), and I think it also had a tie in with the clock module for task switching or something - and that has been split in two as well.
> 
> Bill Nobel has been looking into getting Level III going again with current builds, and has made some progress, but it is not completed (he is also working on fixing >8K grfdrv module sizes so it doesn’t try to initially link it in in the system map, which for quite a few people won’t fit, so it just crashes; and he is also very active on Roger Taylor’s Coco on a Chip family of products, so he, like me, is having our time divided between multiple projects.
> 
> L. Curtis Boyle
> curtisboyle at sasktel.net
> 
> 
> 
>> On May 3, 2018, at 10:06 AM, Allen Huffman <alsplace at pobox.com> wrote:
>> 
>> On May 3, 2018, at 11:01 AM, L. Curtis Boyle <curtisboyle at sasktel.net> wrote:
>>> 
>>> We ran a 1 MB RAM Coco 3 system at work for 10 years.
>> 
>> Did you ever run the Level 3 patches or was that after this?
>> 
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