25 Sep
2020
25 Sep
'20
9:30 p.m.
On Fri, Sep 25, 2020, 9:22 AM Noel Chiappa <jnc(a)mercury.lcs.mit.edu> wrote:
Back in school, we had our machine organization course. When we learned
about 1's complement, the professor said "I've used a lot of machines that
had this. You will likely never see one with it. There are no operational
machines on campus with that." It stuck with me. We had a TOPS-20
machine... the odd turn of phrase was due to a professor that had a board
of unknown origin hanging on the wall that was a rumored to be a CDC or
similar... ah, the mid 80s...
Warner
From: Warner
Losh
I'm pretty sure PDP-10 wasn't 1's
compliment / was 2's compliment..
Just to confirm, I pulled out my PDP-10 Hardware Reference Manual; Vol I -
CPU
(EK-10/20-HR-001), and it does indeed say (pg. 1-12): "The fixed-point
arithmetic instructions use 2's complement representations to do binary
arithmetic." Selah.