Tokyo, February 9, 2001---Fujitsu Laboratories, Ltd. has developed CMOS high-speed circuit technology that enables data transmission at a rate of 5 Gbps over a single twisted pair cable. This technology makes possible the high-speed data transfer required among processors and servers in high-end next generation enterprise systems, even with inexpensive cable.
Fujitsu introduced this innovation at ISSCC 2001 (the 2001 IEEE International Solid-State Circuits Conference), which took place earlier this week in San Francisco.
Background
In recent years, large-scale server systems made up of multiple linked PC servers and/or Unix servers with high-performance processors have started to be used as core enterprise systems. Architectures for such large-scale systems include Shared Memory Multiprocessor (SMP) systems, where multiple processors are linked through buses, and cluster systems, employing a high-speed System Area Network (SAN). Realizing these kinds of systems requires low signal latency and interconnect technology with Gbps-scale data transfer speed among processors or servers (Fig. 1).
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GaAs optical semiconductor components are usually used for this kind of high-speed data transmission. However, not only are they expensive and consume relatively high amounts of power, but the LSI manufacturing process differs from that of CMOS devices, they cannot be incorporated on the same chip, which increases costs. High-speed transmission over low-cost copper cables would appear to be an effective means of solving this problem, but as the signal transmission frequency increases, so too does copper cable signal degeneration. Moreover, if it is not possible to increase the transmission frequency per cable, it is necessary to increase the number of cables, making cable management difficult.
Fujitsu Development Details
Fujitsu Limited and Fujitsu Laboratories have already developed and provided customers with high-speed signal technology that enables a maximum data transfer speed of 2.5 Gbps per cable. Aiming for even higher data transmission speeds, Fujitsu Laboratories has now developed the following circuit technology, which allows twice the amount of information as before to be transmitted over one cable.
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1) Capacity-coupled hybrid circuit that allows bi-directional transmission over a single cable.
Fujitsu's new hybrid circuit accurately extracts the inbound signal when it is multiplexed with multiple signals moving in both directions on a single cable. This circuit is realized on the CMOS itself, without having to attach a transformer or other external component.
2) An echo canceller that compensates for hybrid circuit output error
When a hybrid circuit attempts to extract the desired inbound signal from a bi-directional flow of multiplexed signals, there tends to be an intermixing (echo) with the outbound signal it is sending. To compensate for echo and improve the quality of the inbound signal, Fujitsu developed an echo canceller circuit. In order to be able to cancel the echo for a 2.5 Gbps high-speed signal in real time, this circuit is effective in decreasing the link's signal latency. A further advantage is that it operates correctly even with plesiochronous clocking, which permits a slight differences between the frequency of sender's and recipient's system clocks.
Development of these technologies enabled Fujitsu to achieve high-speed transmission of 2.5 Gbps in both directions - a total of 5 Gbps - over a single 5-meter-long twisted pair cable. Fujitsu also achieved a maximum of 6 ns for the latency generated in the signal transmission area of the CMOS circuit, the lowest level in the industry.
Terminology
1) Interconnect technology: Connection technology for high-speed transmission of data between processors or between servers
2) Plesiochronous clocking
The crystal oscillators that generate the standard frequency of each server differ slightly in the precision of their input clock and their chip's internal clock. Therefore, during high-speed data transmission between servers, it is necessary to offset the discrepancy between their frequencies. In the clock recovery circuit that Fujitsu has developed, the frequency-offset tolerance is 244 ppm, an offset tolerance that is ample for the 100ppm frequency precision of crystal oscillators currently on the market.
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About Fujitsu
Fujitsu Limited (TSE: 6702) is a leading provider of Internet- based information technology solutions for the global marketplace. Comprising over 500 group companies and affiliates worldwide -- including ICL, Amdahl and DMR Consulting -- it had consolidated revenues of 5.26 trillion yen ($49.6 billion) in the fiscal year ended March 31, 2000. Fujitsu's pace-setting technologies, world-class computing and telecommunications platforms, and global corps of over 60,000 systems and services experts make it uniquely positioned to unleash the infinite possibilities of the Internet to help its customers succeed. Altogether, the Fujitsu Group has 188,000 employees and operations in over 100 countries.
Internet: http://www.fujitsu.com/
About Fujitsu Laboratories Ltd.
Founded in 1968 as a wholly owned subsidiary of Fujitsu Limited, Fujitsu Laboratories Limited is one of the premier research centers in the world. With eight laboratories in Japan, one in China and one in the United States, the organization conducts a wide range of basic and applied research in the areas of Multimedia, Personal Systems, Networks, Peripherals, Advanced Materials and Electronic Devices.