decimal computing

[woodelf]

 >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)