In combination with a wheel for a bicycle and the like having an annular rim, a hub rotatable about its axis, and axially offset groups of circumferentially spaced spokes which centrally support the hub on the rim; a wheel decorating ornament comprising an annular, planar sheet of material decorated on opposite sides, axially disposed between the groups of spokes and radially disposed between the rim and the hub.

The Test Access Port and Boundary Scan Architecture

A computer’s memory system is the repository for all the information the computer’s central processing unit (CPU, or processor) uses and produces. A perfect memory system is one that can supply immediately any datum that the CPU requests. This ideal memory is not practically implementable, however, as the three factors of memory capacity, speed, and cost are directly in opposition. By placing smaller faster memories in front of larger, slower, and cheaper memories, the performance of the memory system may approach that of a perfect memory system—at a reasonable cost. The memory hierarchies of modern general-purpose computers generally contain registers at the top, followed by one or more levels of cache memory, main memory (all three are semiconductor memory), and virtual memory (on a magnetic or optical disk). Figure 1 shows a memory hierarchy typical of today’s (1995) commodity systems. Performance of a memory system is measured in terms of latency and bandwidth. The latency of a memory request is how long it takes the memory system to produce the result of the request. The bandwidth of a memory system is the rate at which the memory system can accept requests and produce results. The memory hierarchy improves average latency by quickly returning results that are found in the higher levels of the hierarchy. The memory hierarchy usually reduces bandwidth requirements by intercepting a fraction of the memory requests at higher levels of the hierarchy. Some machines, such as high-performance vector machines, may have fewer levels in the hierarchy—increasing cost for better predictability and performance. Some of these machines contain no caches at all, relying on large arrays of main memory banks to supply very high bandwidth. Pipelined accesses of operands reduce the performance impact of long latencies in these machines. Cache memories are a general solution to improving the performance of a memory system. Although caches are smaller than typical main memory sizes, they ideally contain the most frequently accessed portions of main memory. By keeping the most heavily used data near the CPU, caches can service a large fraction of the requests without needing to access main memory (the fraction serviced is called the hit rate). Caches require locality of reference to work well transparently—they assume that accessed memory words will be accessed again quickly (temporal locality) and that memory words adjacent to an accessed word will be accessed soon after the access in question (spatial locality). When the CPU issues a request for a datum not in the cache (a cache miss), the cache loads that datum and some number of adjacent data (a cache block) into itself from main memory. To reduce cache misses, some caches are associative—a cache may place a given block in one of several places, collectively called a set. This set is content-addressable; a block may be accessed based on an address tag, one of which is coupled with each block. When a new block is brought into a set and the set is full, the cache’s replacement policy dictates which of the old blocks should be removed from the cache to make room for the new. Most caches use an approximation of least recently used

Memory systems

This paper introduces a new hybrid ASIC/FPGA chip architecture that is being developed in collaboration between IBM and Xilinx, and highlights some of the design challenges this offers for designers and CAD developers. We review recent data from both the ASIC and FPGA industries, including technology features, and trends in usage and costs. This background data indicates that there are advantages to using standard ASICs and FPGAs for many applications, but technical and financial considerations are increasingly driving the need for a hybrid ASIC/FPGA architecture at specific volume tiers and technology nodes. As we describe the hybrid chip architecture ,we point out evolving tool and methodology issues that will need to be addressed to enable customers to effectively design hybrid ASIC/FPGAs. The discussion highlights specific automation issues in the areas of logic partitioning, logic simulation, verification, timing, layout and test.

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A hybrid ASIC and FPGA architecture

We take a fresh look at the problems posed by deep submicron (DSM) geometries and re-open the investigation into how DSM effects are most likely to affect future design methodologies. We describe a comprehensive approach to accurately characterize the device and interconnect characteristics of present and future process generations. This approach results in the generation of a representative strawman technology that is used in conjunction with analytical model simulation tools and empirical design data to obtain a realistic picture of the future of circuit design. We then proceed to quantify the precise impact of interconnect, including delay degradation due to noise, on high performance ASIC designs. Having determined the role of interconnect in performance, we then reconsider the impact of future processes on ASIC design methodology.

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Getting to the bottom of deep submicron

Electrical current source circuitry for a bus is described. The circuitry includes transistor circuitry coupled between the bus and ground for controlling bus current, control circuitry coupled to the transistor circuitry, and a controller coupled to the control circuitry for controlling the transistor circuitry. The controller comprises a variable level circuit comprising setting circuitry for setting a desired current for the bus and transistor reference circuitry coupled to the setting circuitry. The variable level circuit provides a first voltage. Voltage reference circuitry provides a reference voltage. Comparison circuitry is coupled to the voltage reference circuitry and to the variable level circuit for comparing the first voltage with the reference voltage. Logic circuitry is responsive to a trigger signal from the comparison circuitry. An output of the logic circuitry is coupled to the control circuitry in order to turn on the transistor circuitry in a manner dependent upon an output of the logic circuitry.

Electrical current source circuitry for a bus

A method, system and computer program product for analyzing and modifying a static timing slack of a timing path in a static timing analysis of a design of an integrated circuit (IC) with a transient power supply are disclosed. A static timing slack analysis is performed at a selected endpoint in an IC to obtain a candidate timing path leading to the endpoint with a worst static timing slack. A transient static timing slack is determined for the candidate timing path for each clock cycle of a clock signal under the transient power supply. The determined transient static timing slack is used to adjust the timing of the IC and to modify the static timing slack of the candidate timing path.

Static timing slacks analysis and modification

A method of, and a system for, determining an extreme value of a voltage dependent parameter of an integrated circuit design is provided. The method includes determining a plurality of current waveforms, each of the plurality of waveforms corresponding to one of a plurality of aggressor objects in the design of the integrated circuit; applying each of the plurality of current waveforms to a subset of the plurality of power bus nodes, the subset of the plurality of power bus nodes being designed to supply power to a corresponding one of the plurality of aggressor objects; determining a plurality of voltage waveforms, each of the plurality of voltage waveforms being at one of the plurality of power bus nodes and corresponding to one of the plurality of current waveforms; using the plurality of voltage waveforms to determine the extreme value.

Voltage dependent parameter analysis

A design structure. The design structure includes: a first set of FETs having a designed first Vt and a second set of FETs having a designed second Vt, the first Vt different from the second Vt; a first monitor circuit containing at least one FET of the first set of FETs and a second monitor circuit containing at least one FET of the second set of FETs; a compare circuit configured to generate a compare signal based on a performance measurement of the first monitor circuit and of the second monitor circuit; a control unit responsive to the compare signal and configured to generate a control signal regulator based on the compare signal; and an adjustable voltage regulator responsive to the control signal and configured to voltage bias wells of FETs of the second set of FETs, the value of the voltage bias applied based on the control signal.

Methods and circuits to reduce threshold voltage tolerance and skew in multi-threshold voltage applications

A pre-driver circuit in an I/O circuit for an integrated circuit performs the combined functions of voltage level shifting, slew rate control, and tri-state capability, in a single circuit to avoid additional delay caused by implementing any combination of these functions in two or more circuits.

Multi-function pre-driver circuit with slew rate control, tri-state operation, and level-shifting

A driver circuit has an input terminal at which a first signal having a first voltage swing is applied, and an output terminal at which: (i) a second signal having a second voltage swing is provided to external circuitry, and (ii) a third signal having a third voltage swing is received from the external circuitry. A level shifter circuit is coupled to the input terminal and translates the first signal to the second signal. The level shifter circuit includes circuitry which regulates the switching rate of the driver circuit. An output circuit is coupled between the level shifter circuit and the output terminal which drives the external circuitry with the second signal received from the level shifter circuit. The output circuit has a floating well, and a bias circuit is coupled between the output terminal and the well of the output circuit. The bias circuit biases the well proportional to the third voltage swing when the third signal is received at the output terminal. A feedback circuit is coupled between the output terminal and the output circuit. The feedback circuit deactivates at least a portion of the output circuit responsive to the third signal being received at the output terminal.

Douglas W. Stout

Papers

Static timing slacks analysis and modification

Voltage dependent parameter analysis

Methods and circuits to reduce threshold voltage tolerance and skew in multi-threshold voltage applications

Multi-function pre-driver circuit with slew rate control, tri-state operation, and level-shifting

Driver circuit configured for use with receiver