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Chapter 20 ½ The Iliac IV System
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capable of solving certain classes of problems with extremely high speed.
1 Laser memory: The B6500 supervises a 1012-bit
write-once read-only laser memory developed by the Precision Instrument
Company. The beam from an argon laser records binary data by burning microscopic
holes in a thin film of metal coated on a strip of polyester sheet, which
is carried by a rotating drum. Each data strip can store some 2.9 billion
bits. A "strip file" provides storage for 400 data strips containing more
than a trillion bits. The time to locate data stored on any one of the
400 strips is 5 s. Within the same strip data can be located in 200 ins.
The read and record rate is four million bits per second on each of two
channels. A projected use of this memory will allow the user to "dump"
large quantities of programs and data into this storage medium for leisurely
review at a later time; hard copy output can optionally be made from files
within the laser memory.
2 ARPA network link; The ARPA network is a group of computer
installations separated geographically but connected by high-speed (50
000 bits/s) data communication
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