how fast were drum memories?

Chuck Guzis cclist at
Thu May 10 14:52:49 CDT 2018

"Fast" is a fuzzy term.

The 865A drum that Paul cited did spin at 1800 RPM, but had a transfer
speed of 2MHz per channel.  Data was transfered in 12-bit parallel, so
the composite transfer speed was 24Mbit/sec, which isn't too shabby for

As it was used as a paging drum, transfer speed was probably more
important than rotational latency.   A page was either 512 or 65,536
64-bit words (4096 bytes or 512K bytes).

The STAR also used 844 disk drives for data storage.

Each "station" had its own "microdrum" of about 72KB that spun at 3600
RPM, but had a transfer rate of 1MHz.  It was used to run code on the
station and also hold the CPU bootstrap.  It was normally loaded from a
CE "suitcase".


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