This paper presents novel processor architecture for HP-processor with nonvolatile/volatile hybrid cache memory. By simulations of high-performance (HP)-processor using MTJs, it has been clarified that total power of the HP-processor using perpendicular-(p-)STT-MRAM can be reduced by over 90 % with little degradation of processor performance. The presented architecture with nonvolatile memory hierarchy will realize the “normally-off computers”.

This paper describes a proposal of non-volatile cache architecture utilizing novel DRAM / MRAM cell-level hybrid structured memory (D-MRAM) that enables effective power reduction for high performance mobile SoCs without area overhead. Here, the key point to reduce active power is intermittent refresh process for the DRAM-mode. D-MRAM has advantage to reduce static power consumptions compared to the conventional SRAM, because there are no static leakage paths in the D-MRAM cell and it is not needed to supply voltage to its cells when used as the MRAM-mode. Besides, with advanced perpendicular magnetic tunnel junctions (p-MTJ), which decreases the write energy and latency without shortening its retention time, D-MRAM is capable of power reduction by replacing the traditional SRAM caches. Considering the 65-nm CMOS technology, the access latencies of 1MB memory macro are 2.2 ns / 1.5 ns for read / write in DRAM mode, and 2.2 ns / 4.5 ns in MRAM mode, while those of SRAM are 1.17 ns. The SPEC CPU2006 benchmarks have revealed that the energy per instruction (EPI) of the total cache memory can be dramatically reduced by 71 % on average, and the instruction per cycle (IPC) performance of the D-MRAM cache architecture degraded only by approximately 4 % on average in spite of its latency overhead.

New FPGA deign using Dopant-Segregated Schottky MOSFET (DSS-MOSFET) and nonvolatile configuration memory (NCM) has been presented. Both of these devices can be fabricated by mature process for mass production. DSS-MOSFET has very low On-state resistance due to the high density dopant at source/drain junction. Therefore, FPGA is one of the best applications for the use of DSS-MOSFET since DSS-MOSFET can effectively improve not only CMOS logic performance but also pass-transistor logic performance. In addition, NCM with large On/Off resistance ratio, such as ionic memory, is adopted to replace SRAM-based configuration memory. Since NCM is fabricated between interconnect layers of CMOS, silicon area is smaller than in the case of SRAM. Furthermore, since NCM is a nonvolatile device, it is possible to reduce the power consumption by cutting off the power supply of unused circuit blocks. We developed a SPICE model of DSS-MOSFET to measure the delay of basic circuit in FPGA, and confirmed about 18% delay improvement for look-up-table with four to six inputs. We also designed physical layout to evaluate the area reduction of configuration memory, and verified the area of NCM is about 2.8X smaller than that of SRAM-based. Twenty largest MCNC benchmarks indicate that 26% improvement in critical path delay on average, and 15% improvement in area delay products on average can be achieved by the use of DSS-MOSFET and NCM.

Three-dimensional integrated circuits (3D-IC) have the potential to reduce interconnect length and improve performance especially in sub-65nm CMOS technologies. This paper describes design and performance analysis of the 3D-IC in sub-65nm CMOS technologies based on the accurate calculation of interconnects delays using 16-core processors as case studies. Performance improvement of the 3D-IC vs. 2D-IC is increased as CMOS scales down, which is consistent with the expected trend. The performance improvement is over 20%. Furthermore, performance of the 3D-IC in 65 nm (or 45 nm) CMOS technology is superior to that of the 2D-IC in 45 nm (or 32 nm) CMOS technology. It indicates that design conversion from 2D-IC to 3D-IC is superior to the CMOS technology migration according to COMS scaling. Reduction in repeater buffers and area overhead is also estimated.

Recent progress of through-silicon-via (TSV) process is so impressive that everyone can expect real 3D-IC era. The most valuable advantages of 3D-IC is decreasing interconnects. Although analysis of this advantages has been reported in some specific case study, the general theory for quantitative analysis has not been studied. In some cases, the advantage of 3D-IC has been overestimated and much different from that of real chip designs expected. This paper presents the qualitative analysis of general 3D-IC design especially for sub-65nm CMOS generation from designers' point of view. What is understood from this paper is how important IC-design is for 3D-IC and how to gain a big advantage of 3D-IC.