A major difference between the A3000 expansion bus in Zorro II mode and the A2000 bus is the absence of the signals /VPA and /VMA, which comprise the 6800/6502 peripheral support mechanism that's part of the 68000 bus interface. This mechanism was never a supported part of the Zorro II specification, however, and it should not be used by any PIC. Any Zorro II PIC that depends on /VPA or /VMA will not work in the A3000 bus. It was, in fact, impossible to legally use this on the A2000 bus. The E clock is, however, supported on the Zorro III bus, though its duty cycle may vary in some situations.
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