Speculation also known as speculative loading, is a process implemented in explicitly parallel instruction computing epic processors and their compiler s to. Peripheral devices are hardware used for input, auxiliary storage, display, and communication. Us5781752a table based data speculation circuit for. In a processor capable of executing program instructions in an execution order differing from their program order, the processor further having a data speculation circuit for detecting data dependence. I built a low profile gaming computer that sits next to his tv. A hardwaresoftware approach for thread level control speculation luong dinh hung, hideyuki miura, chitaka iwama, daisuke tashiro, niko demus barli, shuichi sakai and hidehiko tanaka. Dynamic scheduling from csci 360 at hunter college, cuny. Wide issue and speculation ipc the goal is highperformance. Cisc 662 graduate computer architecture lecture 11 hardware. The stampede approach to threadlevel speculation acm. Hardware and software in this section of notes you will learn about the basic parts of a computer and how they work. Pdf speculation techniques for improving load related. Using hardware checkpoints to support software based speculation.
Speculation to greater ilp 3 components of hwbased speculation. It goes right into the tv, no monitor involved, and the only thing you plug into it is a game pad which also controlls the mouse. Control speculation, data dependence speculation, hardware prefetching, and other speculative mechanisms allow the processor to make forward progress without waiting for long. One promising technique for overcoming this problem is threadlevel speculation tls, which enables the compiler to optimistically create parallel threads despite uncertainty as to whether those threads. Separate bypassing of results from the actual completion of an instruction a speculative instruction allowed to bypass its results to other instructions but cannot.
Cs654 advanced computer architecture lec 8 instruction. Increasing the degree of parallelism using speculative. Adriana wisecsci 360 friday, april 7, 2017 lecture 15. Instructionlevel parallelism and its dynamic exploitation csit. Cisc 662 graduate computer architecture lecture 11. Pdf this paper presents a detailed analysis of the application of hardware transactional memory htm support for loop parallelization with.
Computer architecture 20 carnegie mellon onur mutlu duration. Hardware is the physical components of a computer system e. Dynamic branch prediction to choose which instructions to execute 2. We get high clock rates through pipelining as well as advances in process. Cdb can be a limiting factor multiple cdbs possible, but adds overhead in rs write ports. Application guard protects your device from advanced attacks while keeping you productive. Cisc 662 graduate computer architecture lecture 12. Hardware and software parallelism advance computer architecture. A hardwaresoftware approach for thread level control speculation luong dinh hung, hideyuki miura, chitaka iwama, daisuke tashiro, niko demus barli, shuichi sakai and hidehiko tanaka speculative multithreading is a promising approach that exploits thread level parallelism fromsequentialprograms. Hardware based speculation x jun 15, 2019 computer networks mcqs. Todays microcomputer is in every way a multimedia machine.
Cosc 6385 computer architecture exercises edgar gabriel fall 2007 cosc 6385 computer architecture edgar gabriel hardware based speculation branch prediction reduces direct stalls of branches instructions can be issued using dynamic branch prediction, but could not be executed until the branch outcome was known. Googles futuristic fuchsia os will run android apps zdnet. Hardwarebased isolation windows 10 windows security. What value of each variable should be used if the processor predicts b1 and b2 taken t and executes instructions along the way. Mips r4000 users manual, prentice hall, englewood cliffs, n. Hardware based speculation multiple choice questions mcqs, hardware based. In a processor capable of executing program instructions in an execution order differing from their program order, the processor further having a data speculation circuit for detecting data dependence between instructions and detecting a mis speculation where a data consuming instruction dependent for its data on a data producing instruction of earlier program order, is in fact executed. Finally, the software complexity is minimal as a single developer was.
Using hardwaretransactionalmemory support to implement threadlevel speculation article pdf available in ieee transactions on parallel and distributed systems 292. Overcome control dependence by hardware speculating on outcome of branches and executing program as if. Dynamic scheduling adriana wisecsci 360 friday april 7. Download for offline reading, highlight, bookmark or take notes while you read computer architecture mcqs. Performance of hardwarebased encryption, as compared to softwarebased products, is a primary differentiator disk encryption that is embedded in the hard. Overcome control dependence by hardware speculating on outcome of branches and executing program as if guesses were correct speculation fetch, issue, and execute instructions as if branch predictions were always correct dynamic scheduling only fetches and issues instructions.
May 06, 2019 hardware and software parallelism advance computer architecture aca. Branch prediction reduces direct stalls of branches instructions can be issued using dynamic branch prediction, but could not be executed until the branch outcome was known speculative executions extends the concept of dynamic scheduling. In an outoforder engine, the instruction scheduler is responsible for dispatching instructions to execution units based on dependencies, latencies, and resource. Hardware based speculation quiz questions and answers pdf. Speculat ive memory reads are typical of advanced microprocessors and part of the overall functionality which enables very high performance. A hardwaresoftware approach for thread level control. Finally, the software complexity is minimal as a single developer was able to incorporate atomic regions into a sophisticated 300,000 line code base in three months, despite never having seen the translator source.
However, even though speculation can greatly improve performance, it also increases power dissipation and. To balance the benefits of value prediction with misprediction recovery penalties, some selective value prediction techniques, either hardwarebased dynamic. What value of each variable should be used if the processor. Access the register file and the reorder buffer for the. Speculative execution using return stack buffers arxiv. Hardware and software hardware and software computer hardware includes all the electrical, mechanical, and the electronic parts of a computer. Overview of speculation based cache timing sidechannels. Mar 31, 2009 i also attempt to extract the principles and implicit assumptions behind cryptography and the protection of classified information, as obtained through reverseengineering that is, informed speculation based on existing regulations and stuff i read in books, where they are relevant to technological security. Carnegie mellon computer architecture 983 views 31. A hardwaresoftware approach for thread level control speculation. The system unit contains the electronic components used to process and temporarily store data and instructions figure 3. These components include the central process ing unit, primary memory, and the system board.
Designing the organization and hardware to meet goals and functional requirements and to succeed with changing technology not just isa technology trends. Cosc 6385 computer architecture exercises edgar gabriel fall 2007 cosc 6385 computer architecture edgar gabriel hardware based speculation branch prediction reduces direct stalls of. Chong parallel processing institute, fudan university department of computer science and engineering, university of minnesota at twincities. Cache timing sidechannels are a well understood concept in the area of security research. Task based programming models have demonstrated their efficiency in the development of scientific applications on modern highperformance platforms. Dynamic scheduling with speculation hardware based speculation in lecture. Speculation to allow execution of instructions before control dependences are resolved. Control speculation, data dependence speculation, hardware prefetching, and other speculative mechanisms allow the processor to make forward progress without waiting for longlatency operations to complete. Cisc 662 graduate computer architecture lecture 12 hardware. It goes right into the tv, no monitor involved, and the only thing you plug into it is a. Computer hardware includes computer hardware includes 3 system unit 3 peripheral devices 3 input devices i. Speculation to greater ilp 3 components of hw based speculation.
Dynamic approach hardware based speculation instruction. Dynamic approach hardware based speculation free download as powerpoint presentation. Chapter 3 instructionlevel parallelism and its exploitation ucf cs. A real system evaluation of hardware atomicity for software. Using a unique hardwarebased isolation approach, the goal is to isolate untrusted websites and pdf documents inside a lightweight container that is separated from the operating system via the native windows hypervisor. Googles futuristic fuchsia os will run android apps. Cs654 advanced computer architecture lec 8 instruction level. The novelty of speculationbased cache timing sidechannels is their use of speculative memory reads.
I also attempt to extract the principles and implicit assumptions behind cryptography and the protection of classified information, as obtained through reverseengineering that is, informed. Overview of speculationbased cache timing sidechannels. Hardwarebased speculation usually implemented as a circular buffer store results commit or retirement fifo 4th edition. Overcome control dependence by hardware speculating on outcome of branches and executing program as if guesses were correct speculation fetch, issue, and. The term computer hardware refers to the physical components of a computer, namely keyboard, monitor, mouse, and printer, including the digital circuitry. Oct 12, 2004 hi, im working on a project for a friend of mine. Any part that we can see or touch is the hard ware. Computer hardware is an integral part embedded in all modern day automobiles, microwave ovens, electrocardiograph machines, compact disc players, and other devices.
Hardware based speculation mcqs quiz questions and answers. Taskbased programming models have demonstrated their efficiency in the development of scientific applications on modern highperformance platforms. Dynamic control speculation techniques aim at extracting parallelism from the sequential machine code beyond boundaries of a single basic block of instructions in order to gain as much parallelism as in the dataflow graph. Speculation to allow execution of instructions before control. Extends the idea of dynamic scheduling with three key ideas. Implementations of register renaming described in the literature 5, 8, 11, 7 require a large amount of hardware, tend to increase the cycle time, or both. Download for offline reading, highlight, bookmark or take notes while you read computer networks mcqs. Dont know whether to execute instr3 or instr5 until the cmp is completed instr1 instr2. Hardwarebased encryption like drivetrust transparently encrypts and protects data stored on computer hard drives. Hardware based speculation assume the processor predicts b1 to be taken t and executes.
The hardware necessary is synergistic with other needs and was already available on the commercial product used in our evaluation. They allow delegation of the management of parallelization to the runtime system rs, which is in charge of the data coherency, the scheduling, and the assignment of the work to the computational units. Dynamic control speculation techniques aim at extracting parallelism from the sequential machine code beyond boundaries of a single basic block of instructions in order to gain as much parallelism as in the. This means the special version of art can be installed on a fuchsia device using a.
However, advanced processors can use the values that have been speculatively loaded for further speculation. It is this further speculation that is exploited by the speculation based cache timing sidechannels. Structural hazard occurs when a part of the processors hardware is needed. P1,p2 speculation is incorrect, then the value loaded will be discarded by the hardware. This paper also outlines possible mitigations that can be employed for software designed to run on existingarm processors. Performance of hardwarebased encryption, as compared to softwarebased products, is. The final stage of completion of an instruction, after which merely the result. Speculation also known as speculative loading, is a process implemented in explicitly parallel instruction computing epic processors and their compiler s to reduce processormemory exchanging bottlenecks or latency by putting all the data into memory in advance of an actual load instruction. Pdf evaluating and improving threadlevel speculation in.
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