Mensaje
por CBF » 17 Jun 2018 17:40
A question for hap:
Yesterday you've added a "CPU Divider" to a few Fidelity devices.
How exactly does this feature work?
Let's take the fscc12b as example:
In MACHINE_CONFIG the CPU clock is defined by MCFG_DEVICE_CLOCK(4_MHz_XTAL),
and its "CPU Divider" is set to 4 by default.
If I change this CPU divider to 2 (in the menu Options>Configuration), does this then mean
that now the CPU frequency is indeed 8 MHz, i.e. does it have the same effect as if I would
have used MCFG_DEVICE_CLOCK(8_MHz_XTAL) in MACHINE_CONFIG?
(And setting it to "Disabled" changes the CPU frequency to 16 MHz?)
Does this "CPU Divider" setting have any influence on the chess clock, i.e. does the clock
run faster if I decrease the divider?
And one more question:
For the feag2100 I'm already using a "FAKE" port to switch between 5 and 6 MHz:
PORT_START("FAKE")
PORT_CONFNAME( 0x01, 0x01, "CPU Frequency" ) PORT_CHANGED_MEMBER(DEVICE_SELF, fidel6502_state, eag_cpu_freq, nullptr)
PORT_CONFSETTING( 0x00, "5 MHz" )
PORT_CONFSETTING( 0x01, "6 MHz" )
Could there be any conflict between this "FAKE" port and your "div_config" port (with the "CPU Divider"),
because both of them are changing the CPU frequency?
CBF