{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/73090"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/73090","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"Systematically controlling the error rates in variation-prone networks-on-chip for energy efficiency","abstract":"Networks-on-Chip (NoCs) are prone to within-die process variation as they span the whole chip. To tolerate variation, their voltages (Vdd) carry overprovisioned guardbands. As a result, prior work has proposed to save energy by dynamically managing Vdd, operating at reduced Vdd while occasionally su ering and xing errors. Unfortunately, these proposals use ad-hoc controller designs that may not work under other scenarios and do not provide error bounds. This thesis develops a scheme that dynamically minimizes the Vdd of groups of routers in a variation-prone NoC using formal control-theory methods. The scheme, called Contra, saves substantial energy while guaranteeing the stability and convergence of error rates. Moreover, the scheme is enhanced with a low-cost secondary network that retransmits erroneous packets for higher energy e ciency. The enhanced scheme is called Contra+. Both Contra and Contra+ are evaluated using simulations of NoCs with 64{100 routers. In an NoC with 8 routers per Vdd domain, the proposed schemes reduce the average energy consumption of the NoC by 27%; in a futuristic NoC with one router per Vdd domain, Contra+ and Contra reduce the average energy consumption by 37% and 32%, respectively. The performance impact is negligible. These savings are signi cant over the state-of-the-art. The results categorically state that formal control is essential to attain a stable, scalable, and energy-efficient design. Additionally, it is found that while the secondary network helps Contra+ attain higher energy savings, it has a nonnegligible hardware cost. Hence, Contra is the most cost-effective design.","abstract_html":"Networks-on-Chip (NoCs) are prone to within-die process variation as they span the whole chip. To tolerate variation, their voltages (Vdd) carry overprovisioned guardbands. As a result, prior work has proposed to save energy by dynamically managing Vdd, operating at reduced Vdd while occasionally su ering and xing errors. Unfortunately, these proposals use ad-hoc controller designs that may not work under other scenarios and do not provide error bounds. This thesis develops a scheme that dynamically minimizes the Vdd of groups of routers in a variation-prone NoC using formal control-theory methods. The scheme, called Contra, saves substantial energy while guaranteeing the stability and convergence of error rates. Moreover, the scheme is enhanced with a low-cost secondary network that retransmits erroneous packets for higher energy e ciency. The enhanced scheme is called Contra+. Both Contra and Contra+ are evaluated using simulations of NoCs with 64{100 routers. In an NoC with 8 routers per Vdd domain, the proposed schemes reduce the average energy consumption of the NoC by 27%; in a futuristic NoC with one router per Vdd domain, Contra+ and Contra reduce the average energy consumption by 37% and 32%, respectively. The performance impact is negligible. These savings are signi cant over the state-of-the-art. The results categorically state that formal control is essential to attain a stable, scalable, and energy-efficient design. Additionally, it is found that while the secondary network helps Contra+ attain higher energy savings, it has a nonnegligible hardware cost. Hence, Contra is the most cost-effective design.","abstract_has_math":false,"creators":["Pothukuchi, Raghavendra Pradyumna"],"institution":"University of Illinois at Urbana-Champaign","degree_name":"M.S.","degree_level":"Thesis","degree_discipline":"Computer Science","degree_department":null,"school":null,"contributors":["Torrellas, Josep"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2015,"date_issued":"2015-01-21T19:59:26Z","date_published":"2015-01-21T19:59:26Z","updated_at":"2026-07-22T22:26:07Z","subjects":["Computer Architecture","Reliability","Energy efficiency"],"languages":["en"],"rights":["Copyright 2014 Raghavendra Pradyumna Pothukuchi"],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"http://hdl.handle.net/2142/73090","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Torrellas, Josep"]},{"key":"dc:creator","label":"Author","values":["Pothukuchi, Raghavendra Pradyumna"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2015-01-21T19:59:26Z","2017-01-22T10:15:32Z","2014-12","2015-01-21"]},{"key":"dc:type","label":"Dc Type","values":["text"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Computer Science"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Thesis"]},{"key":"thesis:degree_name","label":"Degree Name","values":["M.S."]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["University of Illinois at Urbana-Champaign"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Computer Architecture","Reliability","Energy efficiency"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["en"]},{"key":"dc:rights","label":"Dc Rights","values":["Copyright 2014 Raghavendra Pradyumna Pothukuchi"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["http://hdl.handle.net/2142/73090"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["Networks-on-Chip (NoCs) are prone to within-die process variation as they span the whole chip. To tolerate variation, their voltages (Vdd) carry overprovisioned guardbands. As a result, prior work has proposed to save energy by dynamically managing Vdd, operating at reduced Vdd while occasionally su ering and xing errors. Unfortunately, these proposals use ad-hoc controller designs that may not work under other scenarios and do not provide error bounds. This thesis develops a scheme that dynamically minimizes the Vdd of groups of routers in a variation-prone NoC using formal control-theory methods. The scheme, called Contra, saves substantial energy while guaranteeing the stability and convergence of error rates. Moreover, the scheme is enhanced with a low-cost secondary network that retransmits erroneous packets for higher energy e ciency. The enhanced scheme is called Contra+. Both Contra and Contra+ are evaluated using simulations of NoCs with 64{100 routers. In an NoC with 8 routers per Vdd domain, the proposed schemes reduce the average energy consumption of the NoC by 27%; in a futuristic NoC with one router per Vdd domain, Contra+ and Contra reduce the average energy consumption by 37% and 32%, respectively. The performance impact is negligible. These savings are signi cant over the state-of-the-art. The results categorically state that formal control is essential to attain a stable, scalable, and energy-efficient design. Additionally, it is found that while the secondary network helps Contra+ attain higher energy savings, it has a nonnegligible hardware cost. Hence, Contra is the most cost-effective design.","Item withdrawn by Laura Spradlin (lspradl2@illinois.edu) on 2014-12-05T17:11:52Z Item was in collections: University of Illinois Theses & Dissertations (ID: 1) No. of bitstreams: 2 Pothukuchi_Raghavendra Pradyumna.pdf: 2697519 bytes, checksum: c06e93f9a071c02f989c1ba7581242d1 (MD5) Pothukuchi_Raghavendra Pradyumna.pdf: 2697510 bytes, checksum: de24e3ad8adcd82236bb0bab0b9e9c58 (MD5)","Made available in DSpace on 2015-01-21T19:59:26Z (GMT). No. of bitstreams: 1 Raghavendra Pradyumna_Pothukuchi.pdf: 2689844 bytes, checksum: 72bd35d68426515996fc837fdba12b2d (MD5)","Embargo set by: Seth Robbins for item 73279 Lift date: 2017-01-21T19:59:39Z Reason: Author requested closed access (OA after 2yrs) in Vireo ETD system","Limited Restriction Lifted for Item 73279 on 2017-01-22T10:15:32Z."]},{"key":"dc:title","label":"Title","values":["Systematically controlling the error rates in variation-prone networks-on-chip for energy efficiency"]}]}],"canonical_facts":{"dc:contributor":["Torrellas, Josep"],"dc:creator":["Pothukuchi, Raghavendra Pradyumna"],"dc:date":["2015-01-21T19:59:26Z","2017-01-22T10:15:32Z","2014-12","2015-01-21"],"dc:description":["Networks-on-Chip (NoCs) are prone to within-die process variation as they span the whole chip. To tolerate variation, their voltages (Vdd) carry overprovisioned guardbands. As a result, prior work has proposed to save energy by dynamically managing Vdd, operating at reduced Vdd while occasionally su ering and xing errors. Unfortunately, these proposals use ad-hoc controller designs that may not work under other scenarios and do not provide error bounds. This thesis develops a scheme that dynamically minimizes the Vdd of groups of routers in a variation-prone NoC using formal control-theory methods. The scheme, called Contra, saves substantial energy while guaranteeing the stability and convergence of error rates. Moreover, the scheme is enhanced with a low-cost secondary network that retransmits erroneous packets for higher energy e ciency. The enhanced scheme is called Contra+. Both Contra and Contra+ are evaluated using simulations of NoCs with 64{100 routers. In an NoC with 8 routers per Vdd domain, the proposed schemes reduce the average energy consumption of the NoC by 27%; in a futuristic NoC with one router per Vdd domain, Contra+ and Contra reduce the average energy consumption by 37% and 32%, respectively. The performance impact is negligible. These savings are signi cant over the state-of-the-art. The results categorically state that formal control is essential to attain a stable, scalable, and energy-efficient design. Additionally, it is found that while the secondary network helps Contra+ attain higher energy savings, it has a nonnegligible hardware cost. Hence, Contra is the most cost-effective design.","Item withdrawn by Laura Spradlin (lspradl2@illinois.edu) on 2014-12-05T17:11:52Z Item was in collections: University of Illinois Theses & Dissertations (ID: 1) No. of bitstreams: 2 Pothukuchi_Raghavendra Pradyumna.pdf: 2697519 bytes, checksum: c06e93f9a071c02f989c1ba7581242d1 (MD5) Pothukuchi_Raghavendra Pradyumna.pdf: 2697510 bytes, checksum: de24e3ad8adcd82236bb0bab0b9e9c58 (MD5)","Made available in DSpace on 2015-01-21T19:59:26Z (GMT). No. of bitstreams: 1 Raghavendra Pradyumna_Pothukuchi.pdf: 2689844 bytes, checksum: 72bd35d68426515996fc837fdba12b2d (MD5)","Embargo set by: Seth Robbins for item 73279 Lift date: 2017-01-21T19:59:39Z Reason: Author requested closed access (OA after 2yrs) in Vireo ETD system","Limited Restriction Lifted for Item 73279 on 2017-01-22T10:15:32Z."],"dc:identifier":["http://hdl.handle.net/2142/73090"],"dc:language":["en"],"dc:rights":["Copyright 2014 Raghavendra Pradyumna Pothukuchi"],"dc:subject":["Computer Architecture","Reliability","Energy efficiency"],"dc:title":["Systematically controlling the error rates in variation-prone networks-on-chip for energy efficiency"],"dc:type":["text"],"thesis:degree_discipline":["Computer Science"],"thesis:degree_level":["Thesis"],"thesis:degree_name":["M.S."],"thesis:institution_name":["University of Illinois at Urbana-Champaign"]},"updated_at":"2026-07-22T22:26:07Z"}