Dean Michael Ancajas

Fort-NoCs: Mitigating the Threat of a Compromised NoC

In this paper, we uncover a novel and imminent threat to an emerging computing paradigm: MPSoCs built with 3rd party IP NoCs. We demonstrate that a compromised NoC (C-NoC) can enable a range of security attacks with an accomplice software component. To counteract these threats, we propose Fort-NoCs, a series of techniques that work together to provide protection from a C-NoC in an MPSoC. Fort-NoCss foolproof protection disables covert backdoor activation, and reduces the chance of a successful side-channel attack by “clouding” the information obtained by an attacker. Compared to recently proposed techniques, Fort-NoCs offers a substantially better protection with lower overheads.

Efficiently tolerating timing violations in pipelined microprocessors

Early prediction of an upcoming timing violation presents a tremendous opportunity to mask the performance overhead of tolerating these faults. In this paper, we explore several techniques for optimizing instruction scheduling in an Out-of-Order pipeline, exploiting this new perspective in robust system design. Compared to recently proposed stall based techniques for tolerating predictable timing violations, we demonstrate a massive reduction in performance overhead, while supporting correct execution in faulty environments (64-97% across different benchmarks).

Proactive aging management in heterogeneous NoCs through a criticality-driven routing approach

The emergence of power efficient heterogeneous NoCs presents an intriguing challenge in NoC reliability, particularly due to aging degradation. To effectively tackle this challenge, this work presents a dynamic routing algorithm that exploits the architecture level criticality of network packets while routing. Our proposed framework uses a Wearout Monitoring System (to track NBTI effect) and architecture-level criticality information to create a routing policy that restricts aging degradation with minimal impact on system level performance. Compared to the state-of-the-art BRAR (Buffered-Router Aware Routing), our best scheme achieves 38%, 53% and 29% improvements on network latency, system performance and Energy Delay Product per Flit (EDPPF) overheads, respectively.

Runtime Detection of a Bandwidth Denial Attack from a Rogue Network-on-Chip

In this paper, we propose a covert threat model for MPSoCs designed using 3rd party Network-on-Chips (NoC). We illustrate that a malicious NoC can disrupt the availability of on-chip resources, thereby causing large performance bottlenecks for the software running on the MPSoC platform. We then propose a runtime latency auditor that enables an MPSoC integrator to monitor the trustworthiness of the deployed NoC throughout the chip lifetime. For the proposed technique, our comprehensive cross-layer analysis indicates modest overheads of 12.73% in area, 9.844% in power and 5.4% in terms of network latency.

Exploring high throughput computing paradigm for global routing

With aggressive technology scaling, the complexity of the global routing problem is poised to rapidly grow. Solving such a large computational problem demands a high throughput hardware platform such as modern Graphics Processing Units (GPU). In this work, we explore a hybrid GPU-CPU high-throughput computing environment as a scalable alternative to the traditional CPU-based router. We introduce Net Level Concurrency (NLC): a novel parallel model for router algorithms that aims to exploit concurrency at the level of individual nets. To efficiently uncover NLC, we design a Scheduler to create groups of nets that can be routed in parallel. At its core, our Scheduler employs a novel algorithm to dynamically analyze data dependencies between multiple nets. We believe such an algorithm can lay the foundation for uncovering data-level parallelism in routing: a necessary requirement for employing high throughput hardware. Detailed simulation results show an average of 4X speedup over NTHU-Route 2.0 with negligible loss in solution quality. To the best of our knowledge, this is the first work on utilizing GPUs for global routing.

Wearout Resilience in NoCs Through an Aging Aware Adaptive Routing Algorithm

Continuous technology scaling has made aging mechanisms, such as negative bias temperature instability and electromigration primary concerns in network-on-chip (NoC) designs. In this paper, we extensively analyze the effects of these aging mechanisms on NoC routers and links. We observe a critical need of a robust aging-aware routing algorithm that not only reduces power-performance overheads caused due to aging degradation, but also minimizes the stress experienced by heavily utilized routers and links. To solve this problem, we propose an aging-aware adaptive routing algorithm and a router microarchitecture that routes the packets along the paths, which are both least congested and experience minimum aging degradation. After an extensive experimental analysis using real workloads, we observe 13% and 12.17% average overhead reduction in network latency and energy-delay product per flit, a 10.4% improvement in performance, and a 60% improvement in mean time to failure using our aging-aware routing algorithm.

Exploring High-Throughput Computing Paradigm for Global Routing

With aggressive technology scaling, the complexity of the global routing problem is poised to rapidly grow. Solving such a large computational problem demands a high throughput hardware platform such as modern Graphics Processing Units (GPU). In this work, we explore a hybrid GPU-CPU high-throughput computing environment as a scalable alternative to the traditional CPU-based router. We introduce Net Level Concurrency (NLC): a novel parallel model for router algorithms that aims to exploit concurrency at the level of individual nets. To efficiently uncover NLC, we design a Scheduler to create groups of nets that can be routed in parallel. At its core, our Scheduler employs a novel algorithm to dynamically analyze data dependencies between multiple nets. We believe such an algorithm can lay the foundation for uncovering data-level parallelism in routing: a necessary requirement for employing high throughput hardware. Detailed simulation results show an average of 4X speedup over NTHU-Route 2.0 with negligible loss in solution quality. To the best of our knowledge, this is the first work on utilizing GPUs for global routing.

HCI-tolerant NoC router microarchitecture

The trend towards massive parallel computing has necessitated the need for an On-Chip communication framework that can scale well with the increasing number of cores. At the same time, technology scaling has made transistors susceptible to a multitude of reliability issues (NBTI, HCI, TDDB). In this work, we propose an HCI-Tolerant microarchitecture for an NoC Router by manipulating the switching activity around the circuit. We find that most of the switching activity (the primary cause of HCI degradation) are only concentrated in a few parts of the circuit, severely degrading some portions more than others. Our techniques increase the lifetime of an NoC router by balancing this switching activity. Compared to an NoC without any reliability techniques, our best schemes improve the switching activity distribution, clock cycle degradation, system performance and energy delay product per flit by 19%, 26%, 11% and 17%, respectively, on an average.

Mitigating NBTI in the physical register file through stress prediction

Degradation of transistor parameter values due to Negative Bias Temperature Instability (NBTI) has emerged as a major reliability problem in current and future transistor generations. NBTI Aging of SRAM cell leads to a lower noise margin, thereby increasing the failure rate. The physical register file, which consists of an array of SRAM cells, can suffer from data loss, leading to system failure. In this paper, we explore a novel approach by investigating NBTI stress and mitigation at the instruction granularity. While a wide range of NBTI stress exists in different registers, the stress induced by specific instructions is highly predictable. Using such a prediction mechanism, we propose an NBTI tolerant power efficient physical register file design. Our approach improves the noise margin in a register file by 20%, 32%, and 125% for the 45nm, 32nm, and 22nm technology nodes, respectively. Overall, we observe 14.8% power saving and a 19.8% area penalty in the register file.

DMR3D: dynamic memory relocation in 3D multicore systems

Three-dimensional Multicore Systems present unique opportunities for proximity driven data placement in the memory banks. Coupled with distributed memory controllers, a design trend seen in recent systems, we propose a Dynamic Memory Relocator for 3D Multicores (DMR3D) to dynamically migrate physical pages among different memory controllers. Our proposed technique avoids long interconnect delays, and increases the use of vertical interconnect, thereby substantially reducing memory access latency and communication energy. Our techniques show 30% and 25% average performance and communication energy improvement on real world applications.