Clock gating

About: Clock gating is a research topic. Over the lifetime, 7838 publications have been published within this topic receiving 107903 citations.

Clock frequency modulation for secure microprocessors.

Abstract: A secure microprocessor is provided with reduced vulnerability to attack. In the past, the secure operation of such processors has been overcome by observing the behavior of the clock used by the processor. Such observations, and the prediction of subsequent clock pulses therefrom, are prevented by modulating the clock by a substantially random function to provide an unpredictable stream of clock pulses. The secure processor is responsive to the unpredictable stream of clock pulses for processing data in accordance with a security algorithm.

Information processing system having power saving control of the processor clock

Abstract: An information processing system operates under a multi-tasking operating system in which each task to be run is assigned a priority level. A Clock Switch (41) is positioned between the Clock Oscillator (50) and the Processor (10). A System Timer (70) establishes periodic intervals of time. At the beginning of each time interval, the System Timer, via an Interrupt Controller (60) and Transition Detector (42), turns ON (if its not already ON) the clock to the Processor by sending a Clock Start Signal to the Clock Switch. A Clock Control Program is assigned the lowest priority such that the Clock Control Program runs if and only if there are no other tasks running. When the Clock Control Program runs, it sends a code to a Register (43), which in turn sends a Clock Stop signal to the Clock Switch, thereby stopping the clock to the Processor. As described above, the System Timer will restart the clock again at the beginning of the next time interval. By stopping the clock to the Processor, the power to and the heat dissipated by the Processor are reduced. In an alternate embodiment, the frequency of the clock signal to the processor is reduced, rather than completely stopping the clock to the Processor.

Emulation system with multiple asynchronous clocks

Abstract: An emulation system includes a clock generation logic for generating multiple asynchronous clocks, where each generated clock's relative phase relationship with respect to all other generated clocks is strictly controlled to speed up the emulation logic evaluation. Unlike statically designed emulator systems known in the prior art, the speed of the logic evaluation in the emulator need not be slowed down to the worst possible evaluation time since the clocking is generated internally in the emulator and carefully controlled. The emulation system does not concern itself with the absolute time duration of each clock, because only the phase relationship among the multiple asynchronous clocks is important. By retaining the phase relationship (and the initial values) among the multiple asynchronous clocks, the speed of the logic evaluation in the emulator can be increased. The RCC clock generation logic comprises a clock generation scheduler and a set of clock generation slices, where each clock generation slice generates a clock. The clock generation scheduler compares each clock's next toggle point from the current time, toggles the clock associated with the winning next toggle point, determines the new current time, updates the next toggle point information for all of the clock generation slices, and performs the comparison again in the next evaluation cycle. In the update phase, the winning slice updates its register with a new next toggle point, while the losing slices merely updates their respective registers by adjusting for the new current time.

Method and apparatus for distributing an optical clock in an integrated circuit

Abstract: A method and an apparatus for optically clocking an integrated circuit in a semiconductor. In one embodiment, a laser is configured to emit infrared laser pulses at a desired clock frequency. The laser pulses are separated into a plurality of split laser pulses, each of which are focused through the back side of a C4 packaged integrated circuit die into P-N junctions distributed throughout the integrated circuit die. Each P-N junction locally generates a photocurrent in response to the split laser beams. Each of the photocurrents are locally converted into voltages and thus into local clock signals, which are used to clock the local area of the integrated circuit. With the presently described optical clocking technique, the local clock signals have extremely low clock skew. The presently described technique may be employed in integrated circuits system-wide, in multi-chip modules, or in an individual integrated circuit. By removing the global clock distribution network from the silicon, the present invention allows chip area used in the prior art for a global clock distribution networks to be used instead for signal routing or allows overall die sizes to be reduced.

A 60 MHz 240 mW MPEG-4 video-phone LSI with 16 Mb embedded DRAM

Abstract: A 240-mW single-chip MPEG-4 videophone LSI with a 16-Mb embedded DRAM is fabricated utilizing a 0.25-/spl mu/m CMOS triple-well quad-metal technology. The videophone LSI is applied to the 3GPP 3G-324M video-telephony standard for IMT-2000, and implements the MPEG-4 video SPL1 codec, the AMR speech codec, and the ITU-T H.223 Annex B multiplexing/demultiplexing at the same time. Three 16-bit multimedia-extended RISC processors, dedicated hardware accelerators, and a 16-Mb embedded DRAM are integrated on a 10.84 mm/spl times/10.84 mm die. It also integrates camera, display, audio, and network interfaces required for a mobile video-phone terminal. In addition to conventional low-power techniques, such as clock gating and parallel operation, some new low-power techniques are also employed. These include an embedded DRAM with optimized configuration, a low-power motion estimator, and the adoption of the variable-threshold voltage CMOS (VT-CMOS). The MPEG-4 videophone LSI consumes 240 mW at 60 MHz, which is only 22% of that for a conventional multichip design. Variable threshold voltage CMOS reduces standby leakage current to 26 /spl mu/A, which is only 17% of that for the conventional CMOS design.