| 11. | In addition to faster components, two significant design improvements were incorporated : base registers and additional hardware instructions.
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| 12. | If register 0 is used as the base register, this becomes an example of " absolute addressing ".
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| 13. | Base registers logically contain a virtual address that points to a word in a code or data bank ( segment ).
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| 14. | This is a map-based register established by the Land Registration ( Scotland ) Act 1979 eventually to replace the Sasine Register.
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| 15. | Operand addresses were determined by adding the contents of the selected base register and the 10-bit displacement field ( m ).
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| 16. | The CPU had 15 index registers, a four-bit field ( x ) allowed selection of one index register as the base register.
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| 17. | Base registers B16-B23 are part of the activity state and are maintained by the Exec with no direct access by the activity.
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| 18. | That can then be used as the base register in a base-plus-offset addressing mode which supplies the low-order 16 or 12 bits.
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| 19. | The base register could contain the start address of an array or vector, and the index could select the particular array element required.
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| 20. | Typical instructions contain a function code, the target ( or source ) register, an index register, a base register and a displacement field.
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