| 31. | When the processor needs to access external memory, it starts placing the address of the requested information on the address bus.
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| 32. | For example, a processor with a 16-bit external address bus can only address 2 16 = 65536 memory locations.
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| 33. | Since the Z80 has a 16-bit address bus, it can only address 64 kB of memory at a time.
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| 34. | The processor address bus was now 16 bits and the instruction set consisted of 8, 16, and 24 bit instructions.
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| 35. | The 6100 has a 12-bit data / address bus, limiting RAM to only 4K words ( 6 KB ).
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| 36. | The external interface consists of a 128-bit data bus and a 43-bit address bus operating at 150 MHz.
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| 37. | It is actually two buses ( not on the diagram ) : an address bus and a memory cells using the data bus.
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| 38. | A further extended version which exposed 31 bits of the address bus was also produced, in small quantities, as the 68012.
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| 39. | Gate-A20 can be enabled or disabled by software to allow or prevent the address bus from receiving a signal from A20.
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| 40. | The biggest difference is that the 6545 may be configured so that it has sole access to the address bus for video memory.
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