In the 1620, the memory is a separate cabinet,
connected bycables
to the CPU cabinet.
The first 20K characters of memory resided in the CPU cabinet, up to 40K
characters of optional add-on memory resided in the external cabinet.
Cheers,
Lee Courtney
CHM 1620 Restoration Team Member
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Posts
Subject: decimal computing
That depends on whether you trust the datapath
between the memory and
the CPU. In the 1620, the memory is a separate cabinet,
connected bycables
to the CPU cabinet. A wise designer would run
parity on that
interconnect.
That's still true: high end "system on a
chip" designs have ECC memory
AND parity (at least) on the buses -- even if they only run inside
the chip.
I don't actually know if there was parity
there. Probably yes, since
As for sign bit per digit, in the 1620 the "sign" bit serves two
purposes -- on the least significant digit it's the sign of the
number, on the most significant digit it's the "this is the last
digit" marker.Not that the 1620 is all that efficient -- at 12
digits per
instruction, code density was pretty low.
I don't think that the code density was that bad since it was a two
address instruction.
If you consider at the time most computers had the power of a 4 function
calculator
with tiny amount of data memory the base machine with 20,000 digit memory
was a lot of memory. What was real inefficient was converting from
internal codes
to external coding like printers, paper tape, punch cards all with
different formats.
(I don't have one, I just read the book about it)