Topic: How to get Z80 CPU clock?

[MIRKOSOFT]

Hi!


I'm not sure if is Z80 CPU in Commodore mode only disabled or turned off.


If is only disabled, is possible to get CPU frequency in MHz?


In assembler of MOS, or also in Z80 asembler (for me for future use in programming Z80 CPU).


Many thanks for every help, reply or comments.


Miro

[Hydrophilic]

The Z80 is disabled in C128 mode when the 8502 is active.  The 8502 is disabled when the Z80 is active.  The only exception seems to be the bug in the MMU that lets you activate both CPUs at the same time, but only in C64 mode.
 
Unless somebody makes a special hardware mod, the Z80 runs effectively at twice the VIC character rate (that is, 1/4 the VIC pixel rate).  So on NTSC with 1.02 MHz clock frequency, Z80 runs at 2.04 MHz.  On PAL which has 0.98MHz clock frequency, the Z80 runs at 1.96 MHz.  Changing VIC settings to run in fast mode only seems to effect 8502... the Z80 does not seem to change speed unfortunately...
 
I think if you want to test for possibility of faster Z80 (through hardware modification) you would have to write a program in Z80 assembly language.