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.

/pdf/a-hybrid-asic-and-fpga-architecture-2m8yin05pw.pdf

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.

/pdf/getting-to-the-bottom-of-deep-submicron-fxddi78iyf.pdf

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 circuit includes a resistance-capacitance (RC) structure connected to a first set of transistors and a second set of transistors that perform the same logical function as the first set of transistors. The first set of transistors have thinner gate oxides than the second set of transistors. The RC structure drains an electric field from the first set of transistors, such that the first set of transistors are on only during initial transistor switching. In other words, the RC structure turns off the first set of transistors after transistor switching is completed. Also, the first set of transistors and the second set of transistors share common inputs and outputs. The first set of transistors exhibit higher tunneling currents than the second set of transistors. The thinner gate oxides of the first set of transistors cause the first set of transistors to exhibit higher device currents than the second set of transistors. The RC structure includes a capacitor connected to a gate of the first set of transistors and a resistor connected to the capacitor and to ground.

Transient gate tunneling current control

An integrated circuit has a power grid and a set of independently switchable voltage islands, together with a system and method for measuring the voltage and history of the voltage on the power grid to determine the correct time to allow a large capacitive load (such as a voltage island) to be switched on to or off the power grid.

Method of switching voltage islands in integrated circuits when a grid voltage at a reference location is within a specified range

A major problem in VLSI system design today is controlling offchp driver characteristics and skew in clock generation as process parameters, temperature, and supply voltage vary. A control circuit methodology has been developed which senses the relative performance of a CMOS chip and transmits a digitally encoded state to offchip driver and clock generation circuits to control their operating characteristics.

For off-chip drivers and clock generation

A structure for processing data on a semiconductor device comprising an input island (14), a processing island (8), and an output island (12) formed on the semiconductor device (18). The input island is adapted to accept a specified amount of data and enable a means for providing a first specified voltage for powering the processing island after accepting the specified amount of data. The processing island is adapted to receive and process the specified amount of data from the input island upon powering the processing island by the first specified voltage. The output island is adapted to be powered by a second specified voltage. The processing island is further adapted to transmit the processed data to the output island upon said powering by the second specified voltage. The first specified voltage is adapted to be disabled thereby removing power from processing island upon completion of transmission of the processed data to the output island.

Douglas W. Stout

Papers

Transient gate tunneling current control

Method of switching voltage islands in integrated circuits when a grid voltage at a reference location is within a specified range

For off-chip drivers and clock generation

Power down processing islands

Puce à circuit intégré personalisée par une bibliothèque pour matrice de portes utilisant des interconnexions locales