On the old CDC 6600 running the Kronos operating system developed by Seymour Cray was a I believe a 60-bit mainframe. It referred to units of storage as PRUs. What was a PRU and how can it be converted to bytes? I read a disk storage device held, for example 200,000 PRUs in the late 1970s. I'm curious to find out what size this is in modern times.
How to convert old CDC mainframe PRUs to bytes?
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Quoted directly from Wikipedia:
Assuming a PRU is one "byte" that would yield (200,000 * 12 / 8) = 300,000 8 bit bytes of storage. This seems a bit "small", even for the day.
According to the description of a disk mass storage unit pictured in the CDC 6400 6500 66000 Reference Manual, it held 500 million bits of data (or about 60MB of 8 bit storage / 40MB 12 bit storage). This was a very large device for the time. I remember working of a VAX 11/70 (super mini) in the early 80's that had three whopping 67MB drives - thought I had died and gone to heaven.
This does not answer what a PRU is but does shed some light on the size of mass storage devices used on "super computers" in the 70's