LectureNotesPartFive

LectureNotesPartFive - xLECTURE NOTES Section Five Insert...

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xLECTURE NOTES Section Five Insert page 56 here. In general DRAM requires 1 transistor per bit SRAM requires 4-6 transistors per bit For a given technology the capacity of DRAM is 4-8 times that of SRAM Cycle time of SRAM is 8-16 times faster than DRAM and also 8-16 times more expensive. Most current computer memory is DRAM Cache memory is SRAM Insert handout pages 59-61 here. Some of the advantages of replacing random logic circuits with ROM: ROM’s are dense, regular, repetitive structures, consequently: They require less time to debug Less time to layout Less time to debug Occupy less space ……than equivalent logic circuits. An example comparing the effects of substituting ROM for logic circuits: Motorola 68000 Zilog Z8000 number of transistors 68000 17500 design time 100 man-months 60 man-months layout time 70 man-months 70 man-months elapsed time to first silicon 30 months 30 months elapsed debugging time 6 months 12 months microprogrammed (used rom) random logic Design changes can be more easily accommodated using ROM’s because only the contents of a memory location need be modified, whereas with random logic, entire wiring patterns and layouts may need to be changed. Now let’s turn our attention to specific architectures, specifically the class of uniprocessors---register machines. As we have stated, the most common, well established style of ext. arch. is the register machine, the so-called vonNeumann model or register model. We are going to continue our generalized study of architecture by studing the architecture of the original vonNeumann model, we will later study microprogramming by microprogramming this vonNeumann model.
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the ext. arch. of the vonNeumann machine main memory of 4096 words with a word length of 40 bits. a repertiore of primarily 1 address instructions of the form, operand…opcode where operand is the address in memory of one of the operands opcode is the operation The second operand is, implicitly, one of the two programmable registers in the processor. These two registers being: An accumulator, which is a general purpose register An arithmetic register which is used basically for multiplication and division. Which register is used is determined by the operation specified in the opcode. Instructions are 20 bits long with a 12 bit address field and an 8 bit opcode field
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LectureNotesPartFive - xLECTURE NOTES Section Five Insert...

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