This paper introduces McPAT, an integrated power, area, and timing modeling framework that supports comprehensive design space exploration for multicore and manycore processor configurations ranging from 90nm to 22nm and beyond. At the microarchitectural level, McPAT includes models for the fundamental components of a chip multiprocessor, including in-order and out-of-order processor cores, networks-on-chip, shared caches, integrated memory controllers, and multiple-domain clocking. At the circuit and technology levels, McPAT supports critical-path timing modeling, area modeling, and dynamic, short-circuit, and leakage power modeling for each of the device types forecast in the ITRS roadmap including bulk CMOS, SOI, and double-gate transistors. McPAT has a flexible XML interface to facilitate its use with many performance simulators. Combined with a performance simulator, McPAT enables architects to consistently quantify the cost of new ideas and assess tradeoffs of different architectures using new metrics like energy-delay-area2 product (EDA2P) and energy-delay-area product (EDAP). This paper explores the interconnect options of future manycore processors by varying the degree of clustering over generations of process technologies. Clustering will bring interesting tradeoffs between area and performance because the interconnects needed to group cores into clusters incur area overhead, but many applications can make good use of them due to synergies of cache sharing. Combining power, area, and timing results of McPAT with performance simulation of PARSEC benchmarks at the 22nm technology node for both common in-order and out-of-order manycore designs shows that when die cost is not taken into account clustering 8 cores together gives the best energy-delay product, whereas when cost is taken into account configuring clusters with 4 cores gives the best EDA2P and EDAP.

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McPAT: an integrated power, area, and timing modeling framework for multicore and manycore architectures

Three-dimensional (3-D) hyperintegration is an emerging technology, which vertically stacks and interconnects multiple materials, technologies, and functional components to form highly integrated micro-nano systems. This 3-D hyperintegration is expected to lead to an industry paradigm shift due to its tremendous benefits. Worldwide academic and industrial research activities currently focus on technology innovations, simulation and design, and product prototypes. Anticipated applications start with memory, handheld devices, and high-performance computers and extend to high-density multifunctional heterogeneous integration of InfoTech-NanoTech-BioTech systems. This paper overviews the 3-D hyperintegration and packaging technologies, including motivations, key technology platforms, status, and perspectives towards commercialization. The challenges associated with the 3-D technologies are addressed, including integration architectures and design tools, yield and cost, thermal and mechanical constraints, and manufacturing infrastructure.

3-D Hyperintegration and Packaging Technologies for Micro-Nano Systems

This paper explores the scalability of in-plane and perpendicular MTJ based STT-MRAMs from 65 nm to 8 nm while taking into consideration realistic variability effects. We focus on the read and write performances of a STT-MRAM based cache rather than the obvious advantages such as the denser bit-cell and zero static power. An accurate MTJ macromodel capturing key MTJ properties was adopted for efficient Monte Carlo simulations. For the simulation of access devices and peripheral circuitries, ITRS projected transistor parameters were utilized and calibrated using the MASTAR tool that has been widely used in industry. 6T SRAM and STT-MRAM arrays were implemented with aggressive assist schemes to mimic industrial memory designs. A constant JC0·RA/VDD scaling scenario was used which to the first order gives the optimal balance between read and write margins of STT-MRAMs. The thermal stability factor ensuring a 10 year retention time was obtained by adjusting the free layer thickness as well as assuming improvement in the crystalline anisotropy. Our studies based on the proposed scaling methodology show that in-plane STT-MRAM will outperform SRAM from 15 nm node, while its perpendicular counterpart requires further innovations in MTJ material in order to overcome the poor write performance scaling from 22 nm node onwards.

A Scaling Roadmap and Performance Evaluation of In-Plane and Perpendicular MTJ Based STT-MRAMs for High-Density Cache Memory

One of the most effective techniques to reduce a processor’s power consumption is to reduce supply voltage. However, reducing voltage in the context of manufacturing-induced parameter variations cancause many types of memory circuits to fail. As a result, voltage scaling is limited by a minimum voltage, often called Vccmin, beyond which circuits may not operate reliably. Large memory structures (e.g., caches) typically set Vccmin for the whole processor. In this paper, we propose two architectural techniques that enable microprocessor caches (L1and L2), to operate at low voltages despite very high memory cell failure rates. The Word-disable scheme combines two consecutive cache lines, to form a single cache line where only non-failing words are used. The Bit-fix scheme uses a quarter of the ways in a cache set to store positions and fix bits for failing bits in other ways of the set. During high voltage operation, both schemes allow use of the entire cache. During low voltage operation, they sacrifice cache capacity by 50% and 25%, respectively, to reduce Vccmin below 500mV. Compared to current designs with a Vccmin of 825mV, our schemes enable a 40% voltage reduction, which reduces power by 85% and energy per instruction (EPI) by 53%

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Trading off Cache Capacity for Reliability to Enable Low Voltage Operation

In this paper we introduce CACTI-D, a significant enhancement of CACTI 5.0. CACTI-D adds support for modeling of commodity DRAM technology and support for main memory DRAM chip organization. CACTI-D enables modeling of the complete memory hierarchy with consistent models all the way from SRAM based L1 caches through main memory DRAMs on DIMMs. We illustrate the potential applicability of CACTI-D in the design and analysis of future memory hierarchies by carrying out a last level cache study for a multicore multithreaded architecture at the 32nm technology node. In this study we use CACTI-D to model all components of the memory hierarchy including L1, L2, last level SRAM, logic process based DRAM or commodity DRAM L3 caches, and main memory DRAM chips. We carry out architectural simulation using benchmarks with large data sets and present results of their execution time, breakdown of power in the memory hierarchy, and system energy-delay product for the different system configurations. We find that commodity DRAM technology is most attractive for stacked last level caches, with significantly lower energy-delay products.

A Comprehensive Memory Modeling Tool and Its Application to the Design and Analysis of Future Memory Hierarchies

This paper describes a 2.3 Billion transistors, 8-core, 16-thread, 64-bit Xeon® EX processor with a 24 MB shared L3 cache implemented in a 45 nm nine-metal process. Multiple clock and voltage domains are used to reduce power consumption. Long channel devices and cache sleep mode are used to minimize leakage. Core and cache recovery improve manufacturing yields and enable multiple product flavors from the same silicon die. The disabled blocks are both clock and power gated to minimize their power consumption. Idle power is reduced by shutting off the unterminated I/O links and shedding phases in the voltage regulator to improve the power conversion efficiency.

A 45 nm 8-Core Enterprise Xeon¯ Processor

This paper describes a dual-core 64-b Xeon MP processor implemented in a 65-nm eight-metal process. The 435-mm2 die has 1.328-B transistors. Each core has two threads and a unified 1-MB L2 cache. The 16-MB shared, 16-way set-associative L3 cache implements both sleep and shut-off leakage reduction modes. Long channel transistors are used to reduce subthreshold leakage in cores and uncore (all portions of the die that are outside the cores) control logic. Multiple voltage and clock domains are employed to reduce power

A 65-nm Dual-Core Multithreaded Xeon® Processor With 16-MB L3 Cache

The 16-way set associative, single-ported 16-MB cache for the Dual-Core Intel Xeon Processor 7100 Series uses a 0.624 mum2 cell in a 65-nm 8-metal technology. Low power techniques are implemented in the L3 cache to minimize both leakage and dynamic power. Sleep transistors are used in the SRAM array and peripherals, reducing the cache leakage by more than 2X. Only 0.8% of the cache is powered up for a cache access. Dynamic cache line disable (Intel Cache Safe Technology) with a history buffer protects the cache from latent defects and infant mortality failures

The 65-nm 16-MB Shared On-Die L3 Cache for the Dual-Core Intel Xeon Processor 7100 Series

A dual-core 64b Xeonreg MP processor is implemented in a 65nm 8M process. The 435mm2 die has 1.328B transistors. Each core has two threads and a unified 1MB L2 cache. The 16MB unified, 16-way set-associative L3 cache implements both sleep and shut-off leakage reduction modes

A Dual-Core Multi-Threaded Xeon Processor with 16MB L3 Cache

A 2.3B transistors, 8-core, 16-thread 64-bit Xeon® EX processor with a 24MB shared L3 cache was implemented in a 45nm 9-metal process. Multiple clock and voltage domains are employed to reduce power consumption. Long channel devices and cache sleep mode are used to minimize leakage. Core and cache recovery improve manufacturing yields and enable multiple product flavors using the same silicon die and package. The disabled blocks are both clock and power gated to minimize their power consumption. Idle power is reduced by shutting off the un-terminated I/O links and shedding phases in the voltage regulator to improve the power conversion efficiency.

J. Chang

Papers

A 45 nm 8-Core Enterprise Xeon¯ Processor

A 65-nm Dual-Core Multithreaded Xeon® Processor With 16-MB L3 Cache

The 65-nm 16-MB Shared On-Die L3 Cache for the Dual-Core Intel Xeon Processor 7100 Series

A Dual-Core Multi-Threaded Xeon Processor with 16MB L3 Cache

A 45nm 8-core enterprise Xeon ® processor