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Chapter 4 - The von Neumann Model. This chapter presents the following content: Putting it all together, the von Neumann Model - 1, the von Neumann Model - 2,. the LC-3 as a von Neumann machine, instruction cycle - overview, types of instruction,. | Chapter 4 The Von Neumann Model Basic components Instruction processing Putting it all together The goal: Turn a theoretical device - Turing’s Universal Computational Machine - into an actual computer . interacting with data and instructions from the outside world, and producing output data. Smart building blocks: We have at our disposal a powerful collection of combinational and sequential logic devices. Now we need a master plan . 4 - The von Neumann Model - 1 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 Memory Processing Unit Input Output MAR MDR ALU TEMP Control Unit PC IR (keyboard) (monitor) 4 - The von Neumann Model - 2 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 228 locations. The LC-3 has an address space of 216 locations - i.e. it uses a 16 bit address. 4 - The von Neumann Model - 3 Memory (continued) Addressability (Byte vs. Word): a word is the basic unit of data used by the processing unit, often multiple bytes; frequently, 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 (imperfectly!) 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 . | Chapter 4 The Von Neumann Model Basic components Instruction processing Putting it all together The goal: Turn a theoretical device - Turing’s Universal Computational Machine - into an actual computer . interacting with data and instructions from the outside world, and producing output data. Smart building blocks: We have at our disposal a powerful collection of combinational and sequential logic devices. Now we need a master plan . 4 - The von Neumann Model - 1 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 Memory Processing Unit Input Output MAR MDR ALU TEMP Control Unit PC IR (keyboard) (monitor) 4 - The von Neumann Model - 2 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: .
