Jun 01, 2012 criticality based load delaying scheme reduces useless computation due to mis speculation on noncritical loads and reduces the dynamic energy consumption by 11. Ieee std 642005 revision of ieee std 642001 ieee standard for verilog hardware description language sponsor design automation standards. 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 speculative executions extends the concept of dynamic scheduling speculates on. The need for fast communication in hardwarebased speculative. Aca 17 appg hardware and software for vliw and epic. Hardware based speculation follows the predicted flow of data values to choose when to execute instructions. The prediction provided by the predictor circuit 33, as will be described, is updated based on historical misspeculations detected by the data. Tomasulos approach and hardware based speculation ppt video. It is important to distinguish between the prediction e. Isbn 0738148512 ss95395 no part of this publication may be reproduced in any form, in an electronic retrieval system or otherwise, without the prior written permission of the publisher. Finally, data dependence speculation has been studied in 7, 8, 17, 18, 24.
A hardware and software based technique, value speculation scheduling vss, combines static instruction level parallelism ilp scheduling techniques with dynamic value prediction hardware. The need for fast communication in hardware based speculative chip multiprocessors. Mcqs on hardware based speculation pdf download ebooks. Since the discovery of spectre, a large number of hardware mechanisms for secure speculation has been proposed. Thread partitioning and value prediction for exploiting speculative. Branch prediction reduces the stalls attributable to branches. The data speculation circuit 30 may then, based on the indication of the predictor circuit 33 stall the execution of a memory operation at the processing units 24 in order to avoid mis speculation.
The paper analyses the hardware implementation of a probabilistic ram based neural network architecture, named hypernet, in terms of system training speed, size, and component cost. Hardwarebased speculation method for executing programs, is. Computer architecture objective type questions and answers. Pdf speculation techniques for high level synthesis of. Data speculation based on addressing patterns identifying dualpurpose register us7266673b2. Todays microcomputer is in every way a multimedia machine. Latticebased publickey cryptography in hardware pdf free. The need for fast communication in hardwarebased speculative chip multiprocessors. Jun 14, 2019 computer architecture multiple choice questions and answers mcqs. Speculative execution via address prediction and data prefetching. Using hardware checkpoints to support software based speculation. Hardware based speculation combines three key ideas. Although this standard states the information and format required of door hardware schedules, it is also typically the same sequence and format used for specifying door hardware sets in project speci.
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 speculative executions extends the concept of dynamic scheduling speculates on the outcome of the branch. Data value speculation in superscalar processors sciencedirect. Pdf speculation techniques for improving load related. Ieee standard for verilog hardware description language. The potential of threadlevel speculation based on value pro. Hardware based speculation mcqs quiz questions and answers.
A directory of objective type questions covering all the computer science subjects. Cs650 computer architecture lecture 71 superscalar and. Bad speculation represents a pipeline slots fraction wasted due to incorrect speculations. While architects understand how to build costeffective parallel machines across a wide spectrum of machine sizes ranging from within a single chip to largescale servers, the real challenge is how to easily create parallel software to effectively exploit all of this raw performance potential. Sohn njit computer science dept cs650 computer architecture example reservation stations name busy op vj vk qj qk dest a load1 load2 add1. Sohn njit computer science dept cs650 computer architecture hardware based speculation speculative execution of insructions before resolving branch split instruction completion into write and commit insruction commit when it is no longer speculative. Hardware implementation for the echo canceller system. This includes slots used to issue uops that do not eventually get retired and slots for which the issuepipeline was blocked due to recovery from an earlier incorrect speculation. Overcome control dependence by hardware speculating on outcome of branches and executing program as if guesses were correct if prediction is wrong it needs a hardware to handle it extension over branch prediction with dynamic scheduling.
Any part that we can see or touch is the hard ware. A special hardware buffer is required for the instruction execution sequence, that holds the. Criticality guided energy aware speculation for speculative. One promising technique for overcoming this problem is threadlevel speculation tls, which enables. A real system evaluation of hardware atomicity for software speculation. A real system evaluation of hardware atomicity for software. To counter these dangers, hunt noted, microsoft is focused on ensuring that its mcus satisfy what the company has outlined as the seven properties of highly secure devices. Hardware handles register dependences between tasks compiler specifies which registers should be communicated between tasks memory speculation for memory dependences hardware detects and resolves misspeculation franklin and sohi, the expandable split window paradigm for exploiting finegrain parallelism, isca 1992.
Criticality based thread predictor makes use of criticality information to speculate across low confidence branches. This paper proposed a hardware and software based scheme for value speculation scheduling. The highly publicized vulnerability uses speculative execution to learn victim secrets by changing cache state. This method of executing programs is essentially a data flow execution. If an untrusted site or pdf document turns out to be malicious, it still remains contained within application guards secure. It examines aspects of the implementation of postquantum pkcs. Effective hardware based data prefetching for highperformance processors. Static instruction scheduling for high per formance on. Hardware based speculation maintains a completely precise exception model even for speculated instructions.
In international conference on parallel architectures and compilation techniques pact, october 1999. Speculation based attacks affect hundreds of millions of computers. Hardware schemes for ilp engs 116 lecture 8 hardware schemes for ilp why in hardware at run time. To address these shortcomings, this work integrates atomic regions into a binary translator composed of codesigned hardware and software. Overview of speculation based cache timing sidechannels. Dynamic instruction scheduling with branch prediction. This thesis is based on the following papers, which are referred to in the text by their. Computer hardware includes computer hardware includes 3 system unit 3 peripheral devices 3 input devices i. A real system evaluation of hardware atomicity for. These attacks typically exploit caches to leak information, using speculative instructions to cause changes to the cache state.
Hardware implementation for the echo canceller system based. Work is done before it is known whether it is actually needed, so as to prevent a delay that would have to be incurred by doing the work after it is known that it is needed. Distinguish between hardware versus software speculation mechanisms free download as word doc. If the prediction was not correct, then recovery takes place. The epic approach is based on the application of massive resources. However, in the hardware synthesis context, we can simply choose to either commit the results or discard them based on the evaluation of the conditions. Have reservation stations where register renaming is possible.
In based on the evaluation of the conditional, one of the results will be discarded and the other committed. Many hardwarebased defense schemes against speculative execution attacks use special mechanisms to protect instructions while speculative, and lift the. Intuitively, more defensive mechanisms are less efficient but can securely execute a larger class of programs, while more permissive mechanisms may offer more performance but require more defensive programming. This book is based on the door and hardware institute dhi standard sequence and format for the hardware schedule. A computer is an electronic device, operating under the control of instructions stored in its own memory, that can accept data, process the data according to specified rules, produce results, and stores the results for future use. Hardware implementation for the echo canceller system based subband technique using tms320c67 dsp kit mahmod. Enjoy the videos and music you love, upload original content, and share it all with friends, family, and the world on youtube. Hardwarebased speculation method for executing programs. Hardware based speculation rmd engineering college. Computer architecture multiple choice questions and. Hardware based speculation execute instructions along predicted execution paths but only commit the results if prediction was correct instruction commit.
Evaluating influence of compiler optimizations on data. The potential of profiling to help value prediction is introduced in. Overcome control dependence by hardware speculating on outcome of branches and executing program as if guesses were correct if prediction is wrong it needs a hardware to handle it extension over branch prediction with dynamic scheduling speculation fetch, issue, and execute instructions as if branch predictions were always correct. Cache speculation sidechannels whitepaper arm developer.
Software tecniues for managing speculation on amd processors 2 introduction speculative execution is a basic principle of all modern processor designs and is critical to support high performance hardware. Contention management for a hardware transactional memory us9619750b2 en 20629. Thanoon mse student school of electronics engineering mosul university mosul, iraq abstractthe acoustic echo cancellation system is very. Hardware based speculation with dynamic scheduling does software based speculation with. In this work, several hardwarebased schemes for partitioning the program into speculative threads.
To this end, we formalize each mechanism in the context. After all, the introduction of new components may cause interactions that change the power activity in the rest of the system in significant ways, which is especially true for speculative hardware. Us5781752a table based data speculation circuit for. The potential of threadlevel speculation based on value. As a result, recent computer architecture research has focused on invisible speculation mechanisms that attempt to block changes in cache state due. Using hardware checkpoints to support software based. Apr 28, 2020 this white paper explains hardware based security techniques and technologies that can improve 1 server platform security and data protection for cloud data centers and edge computing. Static vliw scheduling techniques are used to speculate. Hardware based solutions that protect against such forms of attacks try to prevent any speculative changes to the cache subsystem by delaying them.
Advanced computer architecture vtu notes pdf aca vtu notes sw. Here you can download the advanced computer architecture vtu notes pdf aca vtu notes of as per vtu syllabus. Advanced computer architecture vtu notes pdf aca vtu. Distinguish between hardware versus software speculation. Advance computer architecture 10cs74 alpha college of. Hardware and software hardware and software computer hardware includes all the electrical, mechanical, and the electronic parts of a computer. Control speculation, data dependence speculation, hardware pre. Our goal in this project is to implement speculative execution based on tomasulos algorithm. Jul 23, 2020 recent security vulnerabilities that target speculative execution e.
Lecture 17 lecture 17 speculation wish to move instructions across branches to eliminate possible stalls for better scheduling appropriate. Mar 30, 2021 free pdf download lattice based publickey cryptography in hardware this book describes the effective implementation of public key cryptography pkc to address the security challenges of a vast amount of information generated by an extensive network of connected devices ranging from small rfid tags to powerful desktops. Recently, researchers have discussed techniques to exploit the speculative behavior of x86 processors. Hardware based speculation works better when control flow is unpredictable, and when hardware based branch prediction is superior to software based branch prediction done at compile time. Speculative execution is an optimization technique where a computer system performs some task that may not be needed.
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