3-Instruction Processing

3-Instruction Processing - Instruction processing...

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Unformatted text preview: Instruction processing Instruction processing Tathagata Bhattacharjee Tathagata Bhattacharjee The von Neumann Model The von Neumann Model Memory Processing Unit Input Output MAR MDR ALU TEMP Control Unit PC IR (keyboard) (monitor) Memory: holds both data and instructions Processing Unit: carries out the instructions Control Unit: sequences and interprets instructions Input: external information into the memory Output: produces results for the user Tathagata Bhattacharjee The von Neumann Model The von Neumann Model z Memory Each location has an address and contents Address: bit pattern that uniquely identifies a memory location Contents: bit pattern stored at a given address. analogy: p.o. boxes have fixed numbers, but changing contents. Address Space: The total number of memory locations (boxes) available. eg. a 28 bit address provides an address space of 2 28 locations. Tathagata Bhattacharjee The von Neumann Model The von Neumann Model z Memory (continued) Addressability (Byte vs. Word): a word is the basic unit of data used by the processing unit, often multiple bytes; an instruction must store or retrieve an entire word with a single memory access. Addressability refers to the number of bytes of memory referenced by a given address. Extending the p.o. box analogy with an ISA whose word size is 2 bytes: if we have to deliver wide envelopes, we could convert pairs of the original single-width boxes into new double-wide boxes. we then have the choice of retaining the original numbering scheme, with each of the new boxes keeping both their original addresses (Byte Addressability); or we could renumber them all, giving a single address to each of the wider boxes (Word Addressability). Tathagata Bhattacharjee The von Neumann Model The von Neumann Model z Memory (continued) Accessing memory via the MAR & MDR The Memory Address Register sets up the decoder circuitry in the memory. Read: the contents of the specified address will be written to the Memory Data Register....
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This note was uploaded on 07/15/2011 for the course ECON 2023 taught by Professor Johnson during the Summer '11 term at FAU.

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3-Instruction Processing - Instruction processing...

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