Experimental porting work for the TS2068 and TC2068 Timex spectrum like
systems.

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This port requires a TC2068/TS2068 system with a 64K cartridge configured
with the low 32K RAM and high 32K ROM (or all battery backed RAM also works
of course except maybe in the reboot case)

At the moment you need a DivIDE interface and twister attached to the
machine in order to boot it, as it will load the low 32K from the CF card
boot area. The DivIDE needs to be set to not interfere with boot in order
to run with a TC2068/TS2068 system without the spectrum ROM compatibility
cartridge.

Memory is laid out as follows

Kernel mode

0000-3FFF	Dock RAM	- common and other kernel data
4000-7FFF	Dock RAM	- kernel data
8000-FFFF	Dock ROM	- kernel boot and kernel code

Video updating

0000-3FFF	Dock RAM	- common and other kernel data
				  (including font and video)
4000-7FFF	Home RAM	- screens
8000-FFFF	Dock ROM	- kernel boot and kernel code

User mode

0000-3FFF	Dock RAM	- common and other kernel data
4000-77FF	Home RAM	- screens
7800-FFFF	Home RAM	- user space

(if we kept to the 256 pixel screen we can go to a much bigger user space)


If using with FUSE then create an hdf file for the disk, add a filesystem
image to it and then
	dd if=fuzix.load of=tc2068.hdf bs=1046 seek=1 conv=notrunc

to place it in blocks 1+ after the partition table (in the gap left for loaders)

For real media just change the offset so as not to include the 534 bytes of
header on the hdf file.

Debugging state:
- Still chasing down a possible memory corruption bug that looks irq related
- Need to review the video writes - still lose last byte of yes on ls /bin

Optimizations:
- Turn on interrupt mode during swapping