隨著半導體工藝技術的不斷進步 (technology scaling) ，更多的設計資源不得不用於確保集成電路的時序正確性。這種“面向最壞情況(worstcase-oriented) 的芯片設計方法導致了悲觀保守的芯片設計方案，增加了性能及功耗開銷，減少了工藝進步帶來的效益。 / “優於最壞情況(better-than-worst-case) 的芯片設計方法允許犧牲一定的芯片可靠性 (reliability) 來提高性能以及降低功耗，從而提高計算的能量效率 (energy efficiency) 。“優於最壞情況設計方法的核心思想在於放松對芯片可靠性的硬性需求。既然時序錯誤 (timing error) 在關鍵路徑中的發生頻率並不高，我們可以允許錯誤發生，從而節約用於防止錯誤發生所需要的高額開銷。而當錯誤發生時，再利用錯誤檢測和更正方法(error detection and correction) 來消除錯誤造成的影響。這種無須保證計算過程永遠正確無誤的方法通常被稱作“ 時序推測 (timing speculation) 。然而，不幸的是，由於傳統的“面向最壞情況的設計方法往往導致芯片中存在所謂的“關鍵路徑壁壘(wall of critical paths) ，時序推測技術的有效性在一定程度上受限。 / 為了解決上述問題，我們首先研究了時序推測技術的前提與前景，也就是研究了如何估計時序推測技術能夠帶來的最小和最大效益。此外，我們也研究了時序推測芯片 (timing-speculative circuit) 中的若幹設計優化問題。首先，由於引入時序推測技術能夠提高多電壓 (multi-supply voltage)技術的靈活性，我們闡述了時序推測芯片中的多電壓設計問題，並創造性地提出了一種基於動態規劃 (dynamic programming) 的算法來解決這個問題。此外，我們提出了時序推測芯片中的時鐘差異規劃 (clock skew scheduling) 問題。在考慮了時序錯誤率 (timing error rate) 等因素的影響後，我們設計了新穎有效的方法來解決該問題。最後，鑒於工藝差異(process variation) 和老化效應 (wearout effect) 對芯片時序的影響，而且這種影響很難在設計階段被消除，我們提出了一種實時的時序差異調整(clock skew tuning) 架構。利用精心設計的硬件結構，我們可以實時地收集時序錯誤的信息，相應地調整時鐘差異，從而極大地減弱了時序不確定性對芯片性能的影響。 / As circuit non-idealities inevitably worsen with technology scaling, more design resource has to be incorporated to ensure integrated circuit (IC) timing correctness. Such worst-case-oriented design methodology results in pessimistic designs with considerable power and performance overheads, lessening the benefits provided by technology scaling. / Better-than-worst-case (BTWC) design methodology that allows reliability to be traded off against power and performance was proposed to dramatically improve the computation energy-efficiency. The basic idea behind BTWC design methodology is that, since circuit non-idealities mainly manifest themselves as infrequent timing errors on critical paths of the circuit, we can over-clock operating frequency and/or over-scale supply voltage of the chip to a critical point, where timing errors occur, and achieve error-resilient computations by performing timing error detection and correction. This approach is generally referred to as timing speculation, with which it is not necessary to guarantee “always correct operations. Unfortunately, there is usually a “wall of critical paths in the final implementation of a circuit caused by conventional worst-case-oriented design methodology, suggesting that, given a fixed circuit design, the effectiveness of timing speculation is limited by a fixed threshold beyond which the circuit performance/energy efficiency will drop significantly. / To address the above problem, this thesis first proposes to study the premises and prospects of timing speculation by analyzing the minimum and maximum potential benefits that are achievable by timing speculation techniques. After answering the question posed by the conflict between conventional techniques and timing speculation, this thesis investigates multiple design and optimization problems in timing-speculative circuits. Firstly, as introducing timing speculation capability into circuits can naturally extend the flexibility of multi-supply voltage (MSV) designs to a new horizon, this thesis formulates the MSV design problem for timing-speculative circuits and develops a novel algorithm based on dynamic programming to solve it. Secondly, this thesis develops a general formulation of clock skew scheduling (CSS) problem for timing-speculative circuits, wherein timing error rate and its corresponding impact are explicitly considered, and proposes novel algorithms to tackle this problem. Finally, considering the impact of timing uncertainties caused by process variation and wearout effects, which is very difficult to be modeled and addressed at design stage, this thesis also develops a novel online clock skew tuning framework for timing-speculative circuits. By utilizing an elaborately-designed hardware architecture to collect timing error information and tune clock skews at runtime, variation effects can be effectively mitigated. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Ye, Rong. / Thesis (Ph.D.) Chinese University of Hong Kong, 2014. / Includes bibliographical references (leaves 131-142). / Abstracts also in Chinese.
| Identifer | oai:union.ndltd.org:cuhk.edu.hk/oai:cuhk-dr:cuhk_1077653 |
| Date | January 2014 |
| Contributors | Ye, Rong (author.), Xu, Qiang (thesis advisor.), Chinese University of Hong Kong Graduate School. Division of Computer Science and Engineering, (degree granting institution.) |
| Source Sets | The Chinese University of Hong Kong |
| Language | English, Chinese |
| Detected Language | English |
| Type | Text, bibliography, text |
| Format | electronic resource, electronic resource, remote, 1 online resource (xii, 142 leaves) : illustrations (some color), computer, online resource |
| Rights | Use of this resource is governed by the terms and conditions of the Creative Commons “Attribution-NonCommercial-NoDerivatives 4.0 International” License (http://creativecommons.org/licenses/by-nc-nd/4.0/) |
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