Intel nehalem processor core made FPGA synthesizable
We present a FPGA-synthesizable version of the Intel Nehalem processor core, synthesized, partitioned and mapped to a multi-FPGA emulation system consisting of Xilinx Virtex-4 and Virtex-5 FPGAs. To our knowledge, this is the first time a modern state-of-the-art x86 design with the out-of-order micro-architecture is made FPGA synthesizable and capable of high-speed cycle-accurate emulation. Unlike the Intel Atom core which was made FPGA synthesizable on a single Xilinx Virtex-5 in a previous endeavor, the Nehalem core is a more complex design with aggressive clock-gating, double phase latch RAMs, and RTL constructs that have no true equivalent in FPGA architectures. Despite these challenges, we are successful in making the RTL synthesizable with only 5% RTL code modifications, partitioning the design across five FPGAs, and emulating the core at 520 KHz. The synthesizable Nehalem core is able to boot Linux and execute standard x86 workloads with all architectural features enabled.

title: Inferno: a functional simulation infrastructure for modeling microarchitectural data speculations
abstract: This paper presents key insights and design rationales behind Inferno, a functional simulation construction framework developed at Intel to support execution-driven cycle-accurate performance modeling and simulation of advanced microarchitectural data speculation techniques for future processor designs and explorations. Inferno divides the task of functional simulation into three essential components, namely: (1) context manager of in-flight speculatively executed instructions, (2) stateless emulator of instruction semantics, and (3) a high speed functional simulator capable of booting OS and running large-scale system workloads. These building block components work together in concert via a set of well-architected functional model convergence APIs. With a novel abstraction called speculative domain, the context manager serves effectively as a relational database about the in-flight instructions and on-going speculations. Through a set of functional model usage APIs, the context manager enables performance models to express arbitrary microarchitectural data speculation scenarios. The contribution of this paper is to demonstrate the importance of providing a functional model with modular construction, proper abstraction and expressive APIs for speculative state management. Inferno is such a functional model construction framework and has significantly improved productivity in modeling a variety of sophisticated data speculation microarchitecture techniques.

title: Speculative precomputation: long-range prefetching of delinquent loads
abstract: It attacks program stalls from data cache misses by pre-computing future memory accesses in available thread contexts, and prefetching these data. This technique is evaluated by simulating the performance of a research processor based on the Itanium/sup TM/ ISA supporting Simultaneous Multithreading. Two primary forms of Speculative Precomputation are evaluated. If only the non-speculative thread spawns speculative threads, performance gains of up to 30% are achieved when assuming ideal hardware. However, this speedup drops considerably with more realistic hardware assumptions. Permitting speculative threads to directly spawn additional speculative threads reduces the overhead associated with spawning threads and enables significantly more aggressive speculation, overcoming this limitation. Even with realistic costs for spawning threads, speedups as high as 169% are achieved, with an average speedup of 76%.

title: CPR: Composable performance regression for scalable multiprocessor models
abstract: Uniprocessor simulators track resource utilization cycle by cycle to estimate performance. Multiprocessor simulators, however, must account for synchronization events that increase the cost of every cycle simulated and shared resource contention that increases the total number of cycles simulated. These effects cause multiprocessor simulation times to scale superlinearly with the number of cores. Composable performance regression (CPR) fundamentally addresses these intractable multiprocessor simulation times, estimating multiprocessor performance with a combination of uniprocessor, contention, and penalty models. The uniprocessor model predicts baseline performance of each core while the contention models predict interfering accesses from other cores. Uniprocessor and contention model outputs are composed by a penalty model to produce the final multiprocessor performance estimate. Trained with a production quality simulator, CPR is accurate with median errors of 6.63, 4.83 percent for dual-, quad-core multiprocessors. Furthermore, composable regression is scalable, requiring 0.33x the simulations required by prior regression strategies.

title: Mitosis: A Speculative Multithreaded Processor Based on Precomputation Slices
abstract: This paper presents the Mitosis framework, which is a combined hardware-software approach to speculative multithreading, even in the presence of frequent dependences among threads. Speculative multithreading increases single-threaded application performance by exploiting thread-level parallelism speculatively, that is, executing code in parallel, even when the compiler or runtime system cannot guarantee that the parallelism exists. The proposed approach is based on predicting/computing thread input values via software through a piece of code that is added at the beginning of each thread (the precomputation slice). A precomputation slice is expected to compute the correct thread input values most of the time but not necessarily always. This allows aggressive optimization techniques to be applied to the slice to make it very short. This paper focuses on the microarchitecture that supports this execution model. The primary novelty of the microarchitecture is the hardware support for the execution and validation of precomputation slices. Additionally, this paper presents new architectures for the register file and the cache memory in order to support multiple versions of each variable and allow for efficient rollback in case of misspeculation. We show that the proposed microarchitecture, together with the compiler support, achieves an average speedup of 2.2 for applications that conventional nonspeculative approaches are not able to parallelize at all.

title: Register renaming and scheduling for dynamic execution of predicated code
abstract: To achieve higher processor performance requires greater synergy between advanced hardware features and innovative compiler techniques. Recent advancement in compilation techniques for predicated execution has provided significant opportunity in exploiting instruction level parallelism. However, little research has been done on how to efficiently execute predicated code in a dynamic microarchitecture. In this paper, we evaluate hardware optimizations for executing predicated code on a dynamically scheduled microarchitecture. We provide two novel ideas to improve the efficiency of executing predicated code. On a generic Intel Itanium processor pipeline model, we demonstrate that, with some microarchitecture enhancements, a dynamic execution processor can achieve about 16% performance improvement over an equivalent static execution processor.

title: On Independent Cycles in a Bipartite Graph
abstract: Let G=(V1,V2;E) be a bipartite graph with 2k≤m=|V1|≤|V2|=n, where k is a positive integer. We show that if the number of edges of G is at least (2k−1)(n−1)+m, then G contains k vertex-disjoint cycles, unless e(G)=(2k−1)(n−1)+m and G belongs to a known class of graphs.

title: Output PDF Shaping of Singular Weights System: Monotonical Performance Design
abstract: For a group of stochastic systems whose output probability density function (PDF) is modelled by the B-spline neural networks with singular weights dynamics, the output PDF is controlled towards the desired PDF by an innovative optimization design with monotonically decreasing performance. The controller is developed based on the transformed equivalent non-singular system with sufficient conditions given for the monotonic performance.

title: Novel Parameter Identification by Using a High-Gain Observer With Application to a Gas Turbine Engine
abstract: In this study, a novel identification technique, that is high-gain observer-based identification approach, is proposed for systems with bounded process and measurement noises. For system parameters with abnormal changes, an adaptive change detection and parameter identification algorithm is next presented. The presented technique and algorithm are finally applied to the parameter identification of the gas turbine engine by using the recorded input data from the engine test-bed. The identified parameters and the response curves are desirable. The simulations have proved the effectiveness of the proposed procedure compared with the previous identification approach.

title: Partition of a directed bipartite graph into two directed cycles
abstract: Let D = (V1, V2; A) be a directed bipartite graph with |V1| = |V2| = n ⩾ 2. Suppose that dD(x) + dD(y) ⩾ 3n + 1 for all x ϵ V1 and y ϵ V2. Then D contains two vertex-disjoint directed cycles of lengths 2n1 and 2n2, respectively, for any positive integer partition n = n1 + n2. Moreover, the condition is sharp for even n and nearly sharp for odd n.

title: A Scalable Pipelined Associative SIMD Array with Reconfigurable PE Interconnection Network for Embedded Applications
abstract: This paper describes the FPGA implementation of a specialized SIMD processor array for embedded applications. An alternative to traditional SoC or MPSoC architectures, this array combines the massive parallelism inherent in SIMD architectures with the search capabilities of associative computing, producing a SIMD Processor Array System on a Chip (PASoC) well suited for applications such as data mining and bioinformatics. This paper first describes the architecture of the system, and then the pipelining of the processing elements and the addition of a reconfigurable interconnection network. Finally, the paper concludes with a brief description of a string-matching algorithm that can be used for the applications cited above.