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6.7 Computer Hardware

This section outlines the trends in various computer hardware technologies.

The performance of microprocessors has doubled every 18 months for the last ten years. This is due mainly to improvements in Very Large Scale Integration (VLSI) technology, simplified control logic, parallel processing, and compiler optimization. The trend is likely to continue until the end of this century. The current state of the art for a single processor platform is the DEC 8400/5/300 server with the A21164 chip operating at speeds of 75 MHz (internal) and 300 MHz (external), which is rated at 341 SPECint92 and 513 SPECfp92.

The density of memory has also steadily doubled every 24 months in the last fifteen years (64 Kb/chip to 16 Mb/chip). Access time however, during the same period, has only decreased by a factor of 5 (100 ns to 20 ns). The increasing rate for memory density has shown signs of slowing down in recent months, as the 64 Mb chips still have production problems today.

Hard disk density doubles almost every 29 months. In the early 1980s the most common 5 1/4" full-height disk had a capacity of 10 MB; today it is 2+ GB at 3.5" half height resulting in an increase of two orders of magnitude. Full-height 5 1/4" inch disks at much higher density (9 GB) are also available.

The density increase for optical disks has been much slower. One reason is the price-performance of the electro-magnetic disks. Nonetheless, 4 GB read/write optical disks are available. A newly developed laser modulation technology will reduce write times by one half, which will allow optical disks to compete with hard disks in the future.

The density of Quarter Inch Cartridge (QIC) tapes and Digital Audio Tapes (DAT) have also increased drastically. The 14" tapes used widely until the mid-1980s have almost entirely disappeared today.