On Tue, Feb 25, 2014 at 06:27:35PM +0100, Gerrit Heitsch wrote: >Then the interesting part is how to switch between them without >breaking compatibility to existing Software in plain C64 mode. The >dilemma the C128 designers already faced and _almost_ solved. Well, at least the C128 designers made a honest attempt. Had they hidden the extra VIC-IIe registers in C64 mode, it would have been even better. The C65 booted up in C64 mode and used special "port-knocking" sequence on the VIC-III to switch to C65 mode. The suggested change (disable the character generator ROM independent of the VA14 and VA15 settings) sounds like reinventing the function of the CHAREN bit in C128 mode. IIRC, in C128 mode the CHAREN bit controls the visibility of the character generator ROM. Back on topic: Would it be possible to integrate the DRAM address multiplexer on the PLA replacement, and then integrate the functionality of the C128 MMU to the PLA replacement? This would allow such features as relocating the zero page and the stack. This would be like a poor man's C128, without the VDC, Z80, or 2MHz mode. Marko Message was sent through the cbm-hackers mailing listReceived on 2014-02-26 07:00:02
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