This paper describes an 18-GHz coupled VCO array for low jitter and low phase deviation clock distribution. To reduce the skew, jitter and power consumption associated with clock distribution, the clock is generated by a one-dimensional VCO array in which the oscillating nodes of adjacent VCOs are directly connected with wires. The effects of the wire length and number of unit VCOs in the array are discussed. Both 4-unit and a 2-unit VCO arrays for delivering a clock signal to a 16:1 multiplexor were designed and fabricated in a 90-nm CMOS process. The frequency range of the 4-unit VCO array was 16 GHz to 18.5 GHz while each unit VCO consumed 2 mA.

The paper provides an overview of the circuit techniques for CMOS high-speed I/Os, focusing on the design issues in sub-100 nm standard CMOS. First, we describe the evolution of CMOS high-speed I/O since it appeared in mid 90's. In our view, the surge in the I/O bandwidth we experienced from the mid 90's to the present was driven by the continuous improvement of the CMOS IC performance. As a result, CMOS high-speed I/O has covered the data rate ranging from 2.5 Gb/s to 10 Gb/s, and now is heading for 40 Gb/s and beyond. To meet the speed requirements, an optimum choice of the transceiver architecture and its building blocks are crucial. We pick the most critical building blocks such as the decision circuit and the multiplexors and give detailed explanation of their designs. We describe the low-voltage operation of the high-speed I/O in view of reducing the power consumption. An example of a 90-nm CMOS 2.5 Gb/s transceiver operating off a 0.8 V power supply will be described. Operability at 0.8 V ensures that the circuits will not become obsolescent, even below the 60 nm process node.

Various kinds of new architectures have been proposed to enhance operating performance of the DRAM. This paper reviews these architectures including EDO, SDRAM, RDRAM, EDRAM, and CDRAM. The EDO slightly modifies the output control of the conventional DRAM architecture. Other innovative architectures try to enhance the performance by taking advantage of DRAM's internal multiple bits architecture with internal pipeline, parallel-serial conversion, or static buffers/on-chip cache. A quantitative analysis based on an assumption of wait cycles was made to compare PC system performance with some architectures. The calculation indicated the effectiveness of external or on-chip cache. Future trends cover high-speed I/O interface, unified memory architecture, and system integrated memory. The interface includes limited I/O swing such as HSTL and SSTL to realize more than 100MHz operation. Also, Ramlink and SyncLink are briefly reviewed as candidates for next generation interface. Unified memory architecture attempts to save total memory capacity by combining graphics and main memory. Advanced device technology enables system integration which combine system logic and memory. It suggests one potential direction towards system on a chip in the future.