2 Oct
2024
2 Oct
'24
9:23 p.m.
On Wed, 2024-10-02 at 16:39 -0400, Paul Koning via cctalk wrote:
For the earlier 1311, lack of overlap made perfect
sense. After all,
the 1620 has no interrupts, no parallelism of any kind: every I/O
operation stalls the CPU until the operation is finished. (That and
the BB instruction are among the reasons why Dijkstra rejected the
1620.)
1401 had overlap, but as far as I can tell, only for cards and tape.
The 1403 had a buffer, and 1401 had instructions to test whether the
printer or carriage were busy, but that "overlap" didn't work the same
as for cards and tape.
I remember the 1620 being called CADET, but not because it was a
beginner computer. It didn't have arithmetic hardware. It was done by
table lookup. CADET meant "Can't Add, Doesn't Even Try." One of my
colleagues exploited the table-based arithmetic to do octal arithmetic
for satellite telemetry processing.