hancock4@[EMAIL PROTECTED]
wrote:
> OFF TOPIC:
>
> On the IBM 1401, I heard that one has to issue two "clear storage"
> instructions to totally clear out storage. The first execution clears
> out a ****tion, the second clears out the rest. Something to do with
> the print area, which is a reserved section of storage?
>
> Any explanation would be appreciated.
Monstrously twisted, though one can just barely make out the original
truth through the fog. The CS instruction cleared downward from the
given address through (inclusively) the next lower xxx00 address. So it
would take as many as 160 CS instructions to clear all of storage,
starting at 15999 (or whatever the high address was) and going down by
100s to 99.
The read, punch, and print areas were all reserved, in 1-80, 101-180,
and 201-332. In addition, 0 and 100 were volatile (they were used by the
card reader and card punch), and 87-89, 92-94, and 97-99 were the
(optional) index registers.
--
John W. Kennedy
"The blind rulers of Logres
Nourished the land on a fallacy of rational virtue."
-- Charles Williams. "Taliessin through Logres: Prelude"
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