[Coco] Bubble Memory

[Tormod Volden]

On Tue, Aug 15, 2017 at 5:12 PM, Brett Gordon wrote:
> that limit is done and gone no?  Tormod's spinx card now can map near 64k
> in and out.  I assume it would be trivial now-a-days to add more granular
> banking if one desired, or a crap ton of banked memory.

Yes, the Spinx-512 card (it fits into the cartridge port or MPI, no
modification of the computer) has 16 banks of 32KB. One of them at the
time can be mapped in at 8000-FEFF and one at 0000-7FFF* (could be the
same...). It has some granularity by means of selecting which of the
8KB chunks (in CPU space) are actually mapped (or "visible"). So you
can map one bank high and one bank low, but e.g. only activate
2000-7FFF of the low bank to leave the internal memory available in
0000-1FFF.

*) Because of the way the SAM and the internal memory is wired up, any
writes here scribbles the internal memory, which also needs to hold
the VDU pages. Not much do about that without modifying the computer
internally.

My newer generation card doesn't use above scheme, and is "more
interesting" but not yet available (too busy at the moment).

>
> Actually putting any such scheme to use software-wise would be probably
> more work than the hardware involved.

Yes, indeed. Once you get past the making of a PCB and throwing on a
CPLD, the hardware is rather trivial. But it needs software to become
useful. FUZIX supports the Spinx-512 card, and it would be relatively
easy to make a RAM disk device for NitrOS-9. Using the extra RAM in
BASIC is not straight-forward though.

Tormod