Denial

Mike wrote:I'd suppose not having room for a jump table at a certain address would be the least problem in attempting a port of GEOS.

polluks wrote:Not really, without this RAM area you will lose compatibility, see Apple II GEOS. Stupid design decision.

At least they got it working on the Apple II.

On the VIC-20 without internal mods (as hinted at by me earlier in this thread), 16K of address space ($C000..$FFFF) are permanently lost for own programs. Especially the IRQ, NMI and Reset vectors at $FFFA..$FFFF are fixed, and you'd normally expect an OS to take control over all those three.

Then there's a reduced screen estate of 160x192 pixels (if you take an established bitmap mode on the VIC-20) versus 320x200 pixels on the C64. That could be worked around by redesigning the GUI, sure. But then you could quite as well just write an own OS/GUI from scratch.

And *you* are concerned about the position of some jump table...