Brian W. Curran

Design of the Power6 Microprocessor

The POWER6trade microprocessor combines ultra-high frequency operation, aggressive power reduction, a highly scalable memory subsystem, and mainframe-like reliability, availability, and serviceability. The 341mm2 700M transistor dual-core microprocessor is fabricated in a 65nm SOI process with 10 levels of low-k copper interconnect. It operates at clock frequencies over 5GHz in high-performance applications, and consumes under 100W in power-sensitive applications.

Design methodology for the S/390 parallel enterprise server G4 microprocessors

This paper describes the design methodology employed in the design of the S/390® Parallel Enterprise Server G4 microprocessors. Issues of verifying design metrics of area, power, noise, timing, testability, and functional correctness are discussed within the context of a transistor-level custom design approach. Practical issues of managing the complexity of a 7.8-million-transistor design and encouraging design productivity are introduced.

IBM zEnterprise 196 microprocessor and cache subsystem

The IBM zEnterprise® 196 (z196) system, announced in the second quarter of 2010, is the latest generation of the IBM System z® mainframe. The system is designed with a new microprocessor and memory subsystems, which distinguishes it from its z10® predecessor. The system has up to 40% improvement in performance for traditional z/OS® workloads and carries up to 60% more capacity when compared with its z10 predecessor. The memory subsystem has four levels of cache hierarchy (L1 through L4) and constructs the L3 and L4 caches with embedded DRAM silicon technology, which achieves approximately three times the cache density over traditional static RAM technology. The microprocessor has 50% more decode and dispatch bandwidth when compared with the z10 microprocessor, as well as an out-of-order design that can issue and execute up to five instructions every single cycle. The microprocessor has an advanced branch prediction structure and employs enhanced store queue management algorithms. At the date of product announcement, the microprocessor was the fastest complex-instruction-set computing processor in the industry, running at a sustained 5.2 GHz, executing approximately 1,100 instructions, 220 of which are cracked into reduced-instruction-set computing-type operations, to achieve large performance gains in legacy online transaction processing and compute-intensive workloads.

A 5.2GHz microprocessor chip for the IBM zEnterprise™ system

The microprocessor chip for the IBM zEnterprise 196 (z 196) system is a high-frequency, high-performance design that adds support for out-of-order instruction execution and increases operating frequency by almost 20% compared to the previous 65nm design, while still fitting within the same power envelope. Despite the many difficult engineering hurdles to be overcome, the design team was able to achieve a product frequency of 5.2GHz, providing a significant performance boost for the new system.

Circuit design techniques for the high-performance CMOS IBM S/390 parallel enterprise server G4 microprocessor

This paper describes the circuit design techniques used for the IBM S/390® Parallel Enterprise Server G4 microprocessor to achieve operation up to 400 MHz. A judicious choice of process technology and concurrent top-down and bottom-up design approaches reduced risk and shortened the design time. The use of timing-driven synthesis/placement methodologies improved design turnaround time and chip timing. The combined use of static, dynamic, and self-resetting CMOS (SRCMOS) circuits facilitated the balancing of design time and performance return. The use of robust PLL design, floorplanning, and clock distribution minimized clock skew. Innovative latch designs permitted performance optimization without adding risk. Microarchitecture optimization and circuit innovations improved the performance of timing-critical macros. Full custom array design with extensive use of SRCMOS circuit techniques resulted in an on-chip L1 cache having 2.0-ns cycle time.

Switching codes for delta-I noise reduction

In this paper, we address the off-chip driver delta-I or switching noise problem. We propose a novel approach based on switching codes to reduce this noise. These codes are designed to lower the number of drivers which switch in any given system cycle. A formal theoretic framework for switching codes is developed which provides an upper bound on the number of switching drivers as a function of bit width of the data bus and number of redundant switch bits. Switching codes with error detecting and error correcting capabilities are also presented. Switching codes also reduce the average switching activity and power consumed by the off-chip drivers.

4GHz+ low-latency fixed-point and binary floating-point execution units for the POWER6 processor

A 1-pipe stage, low-latency, 13 FO4, 64b fixed-point execution unit, implemented in a 65nm SOI CMOS process, allows back-to-back execution of data dependent adds, subtracts, compares, shifts, rotates, and logical operations. A 7-pipe stage, 91 FO4, double-precision floating-point unit allows forwarding of dependent results after 6 cycles in most cases

The zEnterprise 196 System and Microprocessor

The zEnterprise 196 is the latest IBM System zSeries mainframe computer, which builds on IBMs 46-year heritage of compatible enterprise-class machines. This design advances the prior z10 processor pipeline with out-of-order execution to achieve considerable performance gains in legacy online transaction processing and computationally intensive workloads. This article describes the system structure and details of this new high-frequency microprocessor.

A 5GHz+ 128-bit Binary Floating-Point Adder for the POWER6 Processor

A fast 128-bit end-around carry adder is designed and fabricated as part of the POWER6 floating-point unit in a 65nm SOI process technology. Efficient use of static circuits and careful balance of the look-ahead tree enable our floating point design to operate beyond 5GHz with 1.1 V supply

IBM eServer z900 high-frequency microprocessor technology, circuits, and design methodology

The IBM eServer z900 microprocessor is a seventh-generation zSeries™ (formerly S/390®) CMOS design which has achieved 1.3-GHz operation. This paper describes the 0.18-µm bulk CMOS, seven-level copper metal process and the high-frequency circuit, integration, and design methodologies developed to achieve this operation. The microprocessor was floorplanned to closely mimic the flow of the microarchitecture pipeline and reduce the communication delay overhead between units. Novel circuit techniques were used in the implementation of the arrays and cache hit detection logic to save power and reduce circuit complexity without sacrificing performance. A four-dimensional gate library and novel synthesis algorithms were developed to yield synthesized control implementations with the performance characteristics of a fully custom circuit design.