The OS chips are new and the?PAL chip?is much easier to replace than the CPU. ?I guess I'll try to replace that first.?
Thanks for the insights.
On Thursday, February 11, 2021, 12:10 AM, mjkirk12 via groups.io <mjkirk12@...> wrote:
K1000 schematic shows 68000 CPU is clocked at 10 MHz (20 MHz oscillator divided by 2).? ?This is 100 nanosecond clock cycle.
If your scope has 20 MHz bandwidth or greater, it may be enough to trigger on DTACK events.
If CPU is accessing non-existent memory ("off the rails"), then DTACK signal will never pulse low.
This would imply the software (code) in the ROM chips is bad,? PAL chip is bad or CPU could be bad.
