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18

TL;DR The ownership issue is really associated with the trademarked brand and product names, and the copyrighted ROM software, not the processor/co-processor hardware. I think there are two mainstream products who's licensing terms are instructive to understanding how the earlier (non-Amiga) Commodore IP has been used and defended by the new rights holders ...


41

I'm trying to identify what kind of machine this is. It looks like an Amiga of some kind, It's a Commodore C64-II also known as C64C: The mouse seams to be an Apple ADB mouse (Type A9M0331), sold from 1986 until the mid 1990s: but I can't read "Amiga" anywhere on the front. Maybe the brand was removed. If you look into the lower right, you'll ...


4

But why are the colors so spread out in the code table? Because these were usable holes in the area of $00..$1F and $80..$9F. Some part was already taken by PET control characters (like Reverse), so everything had to be shifted around - plus, not only colours were added, but function keys as well. Function keys, BTW, provide the only continuous stretch ...


6

As you stated, the results for the C64 make sense, given that the interrupt source is based on a 50 Hz timer which is a bit off from a real 50 Hz signal, like for example the PAL screen refresh. For the Plus/4, both models, the PAL and the NTSC version use a rasterline interrupt as an interrupt source. This can be checked by looking at address $ff0a which ...


2

The video timing is generated by the onboard crystal oscillator. On the C64, the 50/60 Hz clock comes from the stepped down mains frequency of the 9VAC from the transformer, so it ticks at whatever the current mains frequency happens to be. So the C64 clocks are asynchronous. It is not tied to screen refresh. The Plus/4 works differently, it does not use the ...


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