Changes
6502
,/* Interrupt hijacking */
On NMOS, if NMI is asserted during the first 4 ticks of a BRK instruction, the BRK instruction will execute normally at first (PC increments will occur and P will be pushed with the BF flag set), but execution will branch to the NMI vector instead of the IRQ/BRK vector. On CMOS, this situation is correctly handled by executing BRK and then servicing the interrupt.
Similarly, an NMI can hijack an IRQ, and an IRQ can hijack a BRK (though it won't be as visible since they use the same interrupt vector). The tick-by-tick breakdown of all types of interrupts is essentially like that of BRK, save for whether the BF bit is pushed as set and whether PC increments occur.
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