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Topic: Instruction cycle

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	Data processor control unit having an interrupt service using instruction prefetch redirection - Patent 4709324
		The normal instruction prefetches are initiated before the prefetched interrupt instruction or instructions complete execution and before the prefetched interrupt instruction or instructions are decoded to determine whether a most recently prefetched interrupt instruction is a multiple word instruction which is not completely prefetched.
		Eighteen instruction cycles are illustrated in which an interrupt instruction, i, is executed during the execution of instructions n-1, n, n+1 and n+2.
		Whether or not an instruction is a change of flow instruction or a normal instruction may be readily determined from the op code portion of the instruction by instruction decoder 22.
	www.freepatentsonline.com /4709324.html (5494 words)

	week 6 notes [chapter 6 - pipelining] (Site not responding. Last check: 2007-11-03)
		the if/id register is placed where the ir [instruction register] register was, the id/ex register is placed where a and b were, the ex/mem register is placed where aluout was, and the mem/wb register is placed where mdr [memory data register] was.
		so, as we read down the column marked "cycle 3", we know that in the third cycle, the add instruction is in the execute stage, the subtract instruction is in the decode stage, and the "and" instruction is in the fetch stage.
		so in cycle 5, we can grab the value of $1 from the mem/wb pipeline register, and forward it to the alu, where it will be used by the "and" instruction.
	www-cse.ucsd.edu /~j2lau/cs141/week6.html (1846 words)

	nesdev.parodius.com :: View topic - Instruction Cycle Terminology (Site not responding. Last check: 2007-11-03)
		This means that the last cycle of a 4-cycle instruction is the 4th cycle, so in the case of STA $1234, it would be the cycle that writes to address $1234.
		During the sixth cycle, the microprocessor is interpreting the new instruction fetched during cycle 5 while transferring the result of the add operation to the accumulator.
		Instructions utilizing this type of addressing include operations which clear and set bits in the P (Processor Status) register, incrementing and decrementing internal registers and transferring contents of one internal register to another internal register.
	nesdev.parodius.com /bbs/viewtopic.php?t=2065 (919 words)

	BDTI - Buyer's Guide to DSP Processors: Chap. 7
		As used here, ``instruction cycle'' means the time required to execute a single group of one to eight parallel instructions.
		On the TMS320C62xx, one instruction cycle is equal in length to one master clock cycle.
		These instructions perform the indicated arithmetic operation and, in case of overflow, saturate the result to the largest or smallest value that can be represented using 2's complement arithmetic.
	www.bdti.com /products/chap7-17.html (1947 words)

	SPU pipeline examination in the IBM Full-System Simulator for the Cell Broadband Engine processor (Site not responding. Last check: 2007-11-03)
		Valid instructions from the hint buffer will be fed into the predicted path buffer when the hinted instruction (here, the branch at 0x0040c) is loaded into stage "g" of the issue pipeline.
		There is no cross issue (or, the instruction at stage J of issue pipe 0 maps to execution pipe 0, and the instruction at stage J of issue pipe 1 maps to execution pipe 1).
		Instructions are mapped by issue to either pipe 0 (even) or pipe 1 (odd) depending upon the class of instruction (or, the pipelines are asymmetric, having different functional units assigned to each pipeline).
	www.ibm.com /developerworks/power/library/pa-cellspu (4119 words)

	Instruction Processing
		To finish the cycle, the newly fetched instruction is transferred to the instruction register (IR) and unless told otherwise, the CU increments the PC to point to the next address location in memory.
		This is accomplished by using the contents of the instruction register to decide which circuits are to be activated.
		At the completion of the fetched instruction, the control unit updates the program counter to point to the next instruction which is to be fetched.
	users.tinyonline.co.uk /andymc0/instruction_processing.htm (2219 words)

	Instruction cycle - Wikipedia, the free encyclopedia
		The CPU then fetches the instruction from main memory via the data bus into the Current Instruction Register (CIR), a circuit that holds the instruction so that it can be decoded and executed.
		From the instruction register, the data forming the instruction is decoded by the control unit.
		The program is run or executed by retrieving or fetching each instruction from the memory, decoding the operation required and then performing this operation.
	en.wikipedia.org /wiki/Instruction_cycle (369 words)

	Control Unit
		Each instruction cycle is divided into from one to five machine cycles; each machine cycle is in turn divided into from three to five states.
		The number of machine cycle is fixed for a given instruction but varies from one instruction to another.
		The opcode of the current instruction is used to determine which micro-operations to perform during the execute cycle.
	members.tripod.com /Raguraman/cunit.htm (408 words)

	BDTI - DSP Processor Fundamentals Chapter 5
		A single instruction that is to be executed multiple times is loaded into the buffer upon its first execution; immediately subsequent executions of the same instruction fetch the instruction from the cache, freeing the program memory to be used for a data read or write access.
		However, when an instruction is placed in the repeat buffer for repeated execution, the second and subsequent executions of the instruction can perform two memory accesses (one to program memory to fetch one data value and one to data memory to fetch another data value).
		The difference between the single-sector instruction cache and the multi-word repeat buffer is that the cache is loaded with each instruction as it is executed and tracks the addresses of the instructions in the cache.
	www.bdti.com /products/reports_dsppfchap5.htm (7057 words)

	The Fetch-Execute Cycle
		The instruction LDA #7 in the 6502 assembly language means "Load the accumulator with the value 7." It requires two bytes of memory - one to hold the instruction ("Load the accumulator with the byte that follows me in memory") and one to hold the byte itself:
		This instruction is the op-code for STA, which the CPU interprets as meaning "The next number in memory is a one-byte address.
		This means that when X holds the number 0, the instruction is equivalent to LDA 10, when X holds the number 1, the instruction is equivalent to LDA 11, when it holds 2, it is equivalent to LDA 12 etc. The instructions ADC 50,X and STA 80,X work in a similar manner.
	richardbowles.tripod.com /durham/comparch/fetchex.htm (2476 words)

	week 3 notes [chapter 5 - single cycle cpu]
		this is the big disadvantage of single cycle cpu's: the machine must operate at the speed of the slowest instruction.
		update pc: if we executed a branch instruction, and the branch was taken, set the pc to the target of the branch instruction.
		given any instruction, control must direct the flow of bits through the datapath so that the instruction executes properly.
	www-cse.ucsd.edu /~j2lau/cs141/week3.html (945 words)

	Stack Computers: 5.4 ARCHITECTURE OF THE SF1
		Bit 29 in the instruction format can override the selection of TOS as the value to be written by forcing ALUI (which was just loaded on the first half of the clock cycle) to be asserted on the SBUS during the second half of the clock cycle.
		Bit 31 selects an extended instruction cycle, which uses a second clock cycle to access RAM via the MBUS (the first clock cycle is used to fetch the next instruction).
		This first clock cycle is often used to reload the TOS register (which contained an address) with the value to be written into the RAM during the second clock cycle.
	www.ece.cmu.edu /~koopman/stack_computers/sec5_4.html (2004 words)

	Pipelining and the ADR Pseudoinstruction (Site not responding. Last check: 2007-11-03)
		If an instruction requires additional references to memory (for instance reading data from the memory or writing data to the memory) an additional clock phase may be required for each memory reference.
		So while an instruction is being decoded the circuitry that fetches data from the memory may not be in use, and while an instruction is being executed the circuitry that decodes an instruction may be unused.
		Then instructions are generated to either add or subtract an offset to the instruction pointer and store the result in the register specified as the first operand.
	www-edlab.cs.umass.edu /cs201/ADR_pipeline.html (1357 words)

	Variable cycle-time microcomputer - Patent 4509120 (Site not responding. Last check: 2007-11-03)
		A microcomputer is designed having access cycle sequence timing tailored to the requirements of a particular user's peripheral devices through execution of a single instruction.
		While this embodiment envisions the user supplying the parameter during the operation of the microcomputer, it is certainly possible to place the value in the microcomputer during manufacture either on a permanent or semi-permanent manner.
		While the invention has been shown using external hardware relying on the READY lead to modify the access instruction cycle time it is understood that the major value of this concept will be achieved if the microcomputer or microprocessor has the parameter register and control circuitry as a basic part of its internal design.
	www.freepatentsonline.com /4509120.html (2182 words)

	CmpSci 535 Lecture 7
		The instruction fetch unit is basically a device that takes the program counter, presents it to the memory as an address, signals a read cycle on the memory, and latches the memory output to the instruction register.
		Thus we might see two instruction in one word, in which case the fetch unit must be able to realign the second instruction once the first is executed (or the control unit must be able to selectively read part of the IR).
		In the precedig discussion we saw that at least an instruction register is required to deal with the fact that an instruction fetch may not be completed in a single cycle, and also because it is unreasonable to expect the memory to drive the entire data path.
	www.cs.umass.edu /~weems/CmpSci535/535lecture7.html (5016 words)

	instruction cycle definition - Small Business Computing Online Dictionary of IT Terms: Powered by Webopedia (Site not responding. Last check: 2007-11-03)
		The time period during which one instruction is fetched from memory and executed when a computer is given an instruction in machine language.
		There are typically four stages of an instruction cycle that the CPU carries out:
		This step brings the instruction into the instruction register, a circuit that holds the instruction so that it can be decoded and executed.
	sbc.webopedia.com /TERM/I/instruction_cycle.html (176 words)

	Instruction pipeline - Wikipedia, the free encyclopedia
		An instruction pipeline is a technique used in the design of computers and other digital electronic devices to increase their performance.
		Pipelining reduces cycle time of a processor and hence increases instruction throughput, the number of instructions that can be executed in a unit of time.
		If 4 instructions that do not depend on the output of the first instruction are not available, the pipeline control logic must insert a stall or wasted clock cycle into the pipeline until the dependency is resolved.
	en.wikipedia.org /wiki/Instruction_pipeline (1414 words)

	Introduction to DSP - DSP processors: memory architectures
		To fetch the two operands in a single instruction cycle, we need to be able to make two memory accesses simultaneously.
		Note that it is often necessary to fetch three things - the instruction plus two operands - and the Harvard architecture is inadequate to support this: so DSP Harvard architectures often also include a cache memory which can be used to store instructions which will be reused, leaving both Harvard buses free for fetching operands.
		The modified von Neuman architecture allows multiple memory accesses per instruction cycle by the simple trick of running the memory clock faster than the instruction cycle.
	www.bores.com /courses/intro/chips/6_mem.htm (524 words)

	Multiple Issue CPUs
		Each VLIW "instruction" is composed of multiple independent instructions, each of which execute on different function units.
		To control these units, the instruction must allocate 16 or more bits to each unit to describe the operation that the unit will run on each cycle.
		Instruction issue logic is the primary challenge with superscalar.
	www.csee.umbc.edu /~plusquel/611/slides/chap4_6.html (837 words)

	Computation Mini-Instructions (Site not responding. Last check: 2007-11-03)
		We demonstrate the ability of these mini-instructions to express a large number of useful functions and describe simple optimizations which can be performed to speed up the instruction cycle.
		Since the instruction pointer is represented as a machine location, control flow is easily expressed in terms of these primitives.
		Thus, the simplicity and regularity of the instruction set allows a single ADD mini-instruction to be active simultaneously in add, subtract, compare, boolean and jump instructions.
	cdmetcalf.home.comcast.net /papers/milan/node7.html (477 words)

	Instruction Cycle and Instruction Formatting
		The PC is always pointing to the next instruction, even at this level of analysis.
		Much of the execution of the instruction cycle is accomplished by transferring data between registers and activating ALU or memory circuits.
		The pseudocode shown above for the instruction cycle is much like the microprogram.
	faculty.juniata.edu /rhodes/org/ch6incyc.htm (283 words)

	The Water Cycle Instruction Sheet
		The following instruction sheet will guide you so that all sections in this part of our unit can be completed.
		Click on the water cycle power point and view the show.
		Then, number your paper to eight and complete the blank water cycle diagram using the vocabulary words at the end of the slide show.
	www.mtsu.edu /~has2p/watercycleinstructionsheet.htm (385 words)

	MicroProcessor Architectures 7
		The CMP instruction sets condition code bits and the following instruction determines whether the jump is taken and the traget address.
		30% of instructions are branch instructions and with a delay of 3 cycles this reduces the speedup by a factor of 2!
		The delay in the pipeline due to a conditional branch instruction is 4 slots and due to an unconditional instruction 1 slot.
	www.ee.surrey.ac.uk /Teaching/Courses/msccomp/notes/comparch7.html (1735 words)

	Teacher Resources - Lesson Framework
		Using primary sources in research papers and projects is a time-honored way to engage students with primary historical materials.
		Here are ideas for incorporating primary sources into four phases of instruction.
		For example, use a modern newspaper editorial on immigration, minimum wage, or welfare reform as a springboard into exploration of those issues in the past.
	memory.loc.gov /ammem/ndlpedu/lessons/fw.html (1086 words)

	EETimes.com - New DSP architectures work harder
		One method of increasing the amount of work performed by each instruction while maintaining the basics of the traditional DSP architecture and instruction set is to augment the data path with extra execution units.
		Of course, the instruction set must also be enhanced to allow the programmer to specify more parallel operations in each instruction in order to take advantage of the extra hardware.
		DSP processors have traditionally used complex, compound instructions that are issued and executed at the rate of one instruction per instruction cycle.
	www.eetimes.com /story/OEG20000411S0036 (2049 words)

	CSC 317 Notes - Set 8
		Form depends on which of the machine instructions is in the IR May involve transferring data among registers, read/write memory, or invocation of the ALU
		near end of cycle, signal triggers contents of C bus to be stored in one or more registers (even the one that was used for input)
		V1: IFU can interpret each instruction, determine the number of operands that are needed, fetch them and assemble into a register for use by the main execution unit
	courses.dsu.edu /csc317/notes/notset08.htm (1605 words)

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