The expansion bus provides clock signals for expansion boards. The main use for these clocks on Zorro III cards is bus arbitration clocking. There is no relationship between any of these clocks and normal Zorro III bus activity. The relationship between these clocks is illustrated in Figure K-3 . /C1 Clock This is a 3.58 MHz clock (3.55 MHz on PAL systems) that's synched to the falling edge of the 7M system clock. /C3 Clock This is a 3.58 MHz clock (3.55 MHz on PAL systems) that's synched to the rising edge of the 7M system clock. CDAC Clock This is a 7.16 MHz system clock (7.09 MHz on PAL systems) which trails the 7M clock by 90 degrees (approximately 35ns). E Clock This is the 68000 generated "E" clock, used for 6800 family peripherals driven by "E" and 6502 peripherals driven by phi(2). This clock is four 7M clocks high, six clocks low, as per the 68000 spec. 7M Clock This is the 7.16 MHz system clock (7.09 MHz on PAL systems). This clock drives the bus master registration mechanism for Zorro III bus masters.