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9

On a C64 PAL model, the VIC chip processes through 312 lines where each lines takes 63 clock cycles to display (including some time for horizontal and vertical blanking for returning the raster beam). So, if a timer counting every clock cycle is once synchronized to the beginning of rasterline 0, then the timer value t tells us the number of the current line ...


3

https://www.codebase64.org/doku.php?id=base:using_a_timer_as_an_inverted_raster_x-pos_register_method The link describes, basically: first, how to synchronize timer to the raster interrupt; second, how to use that synchronized timer that counts from 0 to 6, to get the CPU in "hard" (i.e. cycle-exact) sync with the beam position. This link and the described ...


21

The change in the MOS designator from 65xx to 85xx was due to the process change - original 65xx were NMOS process, while later 85xx changed to the new HMOS process. This allowed for better densities and lower power dissipation. A positive benefit being that the 85xx used less power even at higher speeds, with obvious benefits for cooling, PSU budget, and ...


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