21. A 13-bit address bus , as illustrated here, is suitable for a device up to 128 Mbit. 22. The address bus was 16-bits wide in the initial implementation and later extended to 24-bits wide. 23. Bank switching can be considered as a way of extending the address bus of a processor with some external register. 24. Combined with the two address bus sizes this meant that the chip was offered in a total of four versions: 25. Again the restrictions of the 16 bit address bus still meant memory banking was a necessity for memory greedy applications. 26. The 6800 had a three-state control that would disable the address bus to allow another device direct memory access. 27. If I have n wires in my address bus , I can address up to 2 ^ n chunks of memory. 28. Also, there were not enough pins available on a low cost 40-pin package for the additional four address bus pins 29. It was an 8-bit CPU with an external 14-bit address bus that could address 16 KB of memory. 30. The original 68000 ( introduced in 1979 ) had a 24-bit address bus and a 16-bit data bus.
