[Coco] any interest in an 8MB ram card for COCO3?
Boisy G. Pitre
boisy at tee-boy.com
Fri Apr 16 16:41:25 EDT 2010
On Apr 16, 2010, at 3:35 PM, Stephen Adolph wrote:
> I think I can make it work in the 512k upgrade position, or at least I
> am giong to try. To be honest I have not done the design right, so I
> am still figuring it out.
> But, what I really want, is to understand if Nitros-9 will support MMU
> bits extention up to 8MB.
NitrOS-9 currently doesn't support beyond 2MB. Paul Barton modified the kernel to support 8MB, and I'm sure his changes could be integrated into NitrOS-9, but I'm not sure (a) how extensive the changes are and (b) how the changes affect performance. I'm not inclined to modify the kernel for experimental cards that aren't available to everyone, but if an 8MB memory card made its way on the CoCo market, I would be willing to look into how NitrOS-9 could accommodate it.
I will say this: 8MB of RAM is pretty impractical given the 64K system ram limit of NitrOS-9 Level 2. You'll have more memory to load modules, and that's about it. My guess is you will run out of system RAM just by the O.S. allocating data structures like path and process descriptors before you can use the whole 8MB in any meaningful way.
> If not, then all I am doing is making a 2MB card.
There's a certain amount of work that will go into either a 2MB card or 8MB card. 2MB will work right away with NitrOS-9 since the two additional MMU bits are in the same register as the working 6 for 512K (and assuming your design works that way).
> Maybe this degenerates into me making myself a 512k card!
Good luck, and keep us posted on your progress.
> On Fri, Apr 16, 2010 at 4:29 PM, Boisy G. Pitre <boisy at tee-boy.com> wrote:
>> On Apr 16, 2010, at 1:47 PM, Stephen Adolph wrote:
>>> If Nitros-9 won't be extended to address more memory then there is no
>>> point I suppose. The scope of what I am thinking of is a RAM card
>>> only - no software, no application...just a RAM subsystem...Steve
>> Welding the card to the CoCo 3 motherboard would require additional logic for MMU bits, and would be much more than simply plugging it into the 512K memory board connectors. I think you would find it much more useful (and easier) to interface it to the cartridge connector and position it as a huge RAM disk.
>> Boisy G. Pitre
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Boisy G. Pitre
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