In this study, we designed and tested dynamically reconfigurable AND/OR and NAND/NOR single flux quantum (SFQ) logic gates. The measured dc bias margins at low frequency were 99-126% and 121-144% for AND/OR and NAND/NOR gates, respectively. The experimentally confirmed maximum operating frequencies of the AND/OR and NAND/NOR gats were 36 GHz and 24 GHz, respectively. We investigated a circuit design method that enables the efficient design of SFQ logic circuits by using dynamically reconfigurable SFQ logic gates. The logic circuits were designed with a small number of gates using the input data pattern dependence of the Boolean function and reconfiguring the dynamically reconfigurable SFQ logic gates. As a case study, we designed and tested a bit-serial SFQ full adder using the investigated circuit design method. Compared with the conventional bit-serial SFQ full adder, the delay of the proposed full adder was reduced by 27%, assuming a clock frequency of 20 GHz. We confirmed correct operation of the adder with a low-speed test. Index Terms-Single flux quantum circuit, reconfigurable logic device, full adder.
The Broadcom BCM12500 is a high performance system on a chip (SOC) targeted at network centric tasks. The chip consists of two high performance SB-1 MIPS64m CPU's, a shared 512KB L2 cache, a DDR memory controller, and integrated UO. All major blocks of the processor are connected together via the ZBbusTM; a high speed split transaction fully coherent multi processor bus.Three Gigabit Ethernet MAC's enable a direct interface to network elements. High-speed system U 0 is provided using AMD's Lightning Data Transport (LDTm) U 0 fabric and a 66MHz PCI bus. The die measures 14.2" by 13.3" in a bulk 0.15pm CMOS technology and has a power dissipation of 13W at 1.2V and 1GHz.
A single-flux-quantum (SFQ) arithmetic logic unit (ALU) was designed and tested to evaluate the effectiveness of introducing dynamically reconfigurable logic gates in the design of a superconducting logic circuit. We designed and tested a bit-serial SFQ ALU that can perform six arithmetic/logic functions by using a dynamically reconfigurable AND/OR gate. To ensure stable operation of the ALU, we improved the operating margin of the SFQ AND/OR gate by employing a partially shielded structure where the circuit is partially surrounded by under-and over-ground layers to reduce parasitic inductances. Owing to the introduction of the partially shielded structure, the operating margin of the dynamically reconfigurable AND/OR gate can be improved without increasing the circuit area. This ALU can be designed with a smaller circuit area compared with the conventional ALU by using the dynamically reconfigurable AND/OR gate. We implemented the SFQ ALU using the AIST 2.5 kA/cm 2 Nb standard process 2. We confirmed high-speed operation and correct reconfiguration of the SFQ ALU by a high-speed test. The measured maximum operation frequency was 30 GHz. key words: SFQ circuit, shielding, arithmetic logic unit, reconfigurable logic device
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