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I'm reading a paper about the architecture of the IBM system/360. There is a diagram which lays out the machine structure and implementation in the storage and control tables there is a metric which I don't understand which is Cycle \$\mu\$s:

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What is this metric referring to ? Thanks for the help.

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  • \$\begingroup\$ CYCLE means "machine cycle". 1 us machine cycle means that the machine was operating at 1 MHz clock rate. \$\endgroup\$ Apr 10, 2020 at 1:44

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Ferrite core memory has to be read and then rewritten to retrieve data as the read operation is destructive.

The time to do this read followed by a write is referred to as the cycle time and is typically in the region of one microsecond to a few microseconds as shown in the right-hand column.

The Greek letter mu is the symbol shown to represent micro.

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That's the cycle time of the CPU's memory (in microseconds)!

Yes, these memory systems ran at anywhere from 400 kHz to 1 MHz. Not exactly what you picture for "big iron" nowadays. You can add a column for bandwidth to the table:

MODEL   WIDTH   CYCLE   BANDWIDTH
-----   -----   -----   ---------
 30     8 bits  2.0 us  500 kB/sec
 40    16 bits  2.5 us  800 kB/sec
 50    32 bits  2.0 us  2.0 MB/sec
 60    64 bits  1.0 us  8.0 MB/sec
 70    64 bits  1.0 us  8.0 MB/sec
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