On Sun, 8 Sep 2013 09:58:29 -0700, Jon Perryman wrote:
>WOW. How did it use drum as main memmory? Did it have like 1K of real memory
>and have hardware to move from drum upon address resolution? Or is drum a
>similar architecture to ram?
>
Nope. None of the above. The drum was "real". From:
http://en.wikipedia.org/wiki/IBM_650#Hardware
The rotating drum memory provided 2,000 signed 10-digit words of memory ...,
which is approximately 8.5 KB in today's units.
...
A word could not be accessed until its location on the drum surface passed
under the
read/write heads during rotation (rotating at 12,500 rpm, the non-optimized
average
access time was 2.5 ms). ...
That's ms, not μs.
Programs could be optimized by placing instructions around the drum based
on the
expected execution time of the previous instruction.
-- gil
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