[-- Attachment #1: Type: text/plain, Size: 890 bytes --] On Wednesday, 23 September 2020 at 22:33:38 -0400, Clem Cole wrote: > Dave: Seymour used ones complement on the 3000 and 6000 series. > Maybe there? The primary HLLs I used on the CDC boxes were FTN and > Pascal, but I would not be surprised if that was were you saw it. I think most of the bigger pre-IBM 360 machines used one's complement. Didn't the PDP-10? I knew it not only from the CDC 3200 and 3800, but primarily from Univac (1108 and 494). The Univac techies explained to me that the primary arithmetic function was subtraction; addition was subtracting the complement. And that worked faster with one's complement. Greg -- Sent from my desktop computer. Finger grog@lemis.com for PGP public key. See complete headers for address and phone numbers. This message is digitally signed. If your Microsoft mail program reports problems, please read http://lemis.com/broken-MUA [-- Attachment #2: signature.asc --] [-- Type: application/pgp-signature, Size: 163 bytes --]
[-- Attachment #1: Type: text/plain, Size: 842 bytes --] On Thu, Sep 24, 2020 at 6:20 PM Greg 'groggy' Lehey <grog@lemis.com> wrote: > On Wednesday, 23 September 2020 at 22:33:38 -0400, Clem Cole wrote: > > Dave: Seymour used ones complement on the 3000 and 6000 series. > > Maybe there? The primary HLLs I used on the CDC boxes were FTN and > > Pascal, but I would not be surprised if that was were you saw it. > > I think most of the bigger pre-IBM 360 machines used one's complement. > Didn't the PDP-10? I knew it not only from the CDC 3200 and 3800, but > primarily from Univac (1108 and 494). The Univac techies explained to > me that the primary arithmetic function was subtraction; addition was > subtracting the complement. And that worked faster with one's > complement. > Don't know about the others, but I'm pretty sure PDP-10 wasn't 1's compliment / was 2's compliment.. Warner [-- Attachment #2: Type: text/html, Size: 1278 bytes --]
[-- Attachment #1: Type: text/plain, Size: 1038 bytes --] On Thu, Sep 24, 2020 at 8:22 PM Warner Losh <imp@bsdimp.com> wrote: Don't know about the others, but I'm pretty sure PDP-10 wasn't 1's >> compliment / was 2's compliment.. > > Correct. The PDP-1 (18 bits) was DEC's 1's complement machine. Its direct successors the 4/7/9/15 had both 1's and 2's complement arithmetic. The 12-bit 5/8/12 machines had only 2's complement, but retained the PDP-4 mnemonic TAD (Two's-complement Add). By the time the 36-bit 6/10/20 line was designed, it was clear that 1's complement was history, and the mnemonic was changed to ADD. (The PDP-3 was a PDP-1 with a 36-bit data path, and only one ever went into production; the PDP-2 was to be a 24-bit machine, perhaps a compromise between 6-bit and 8-bit byte systems, but was never even designed.) John Cowan http://vrici.lojban.org/~cowan cowan@ccil.org I marvel at the creature: so secret and so sly as he is, to come sporting in the pool before our very window. Does he think that Men sleep without watch all night? --Faramir [-- Attachment #2: Type: text/html, Size: 1841 bytes --]
> 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. Noel
[-- Attachment #1: Type: text/plain, Size: 913 bytes --] On Fri, Sep 25, 2020, 9:22 AM Noel Chiappa <jnc@mercury.lcs.mit.edu> wrote: > > 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. > 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 > [-- Attachment #2: Type: text/html, Size: 1533 bytes --]
[-- Attachment #1: Type: text/plain, Size: 1014 bytes --] The DECSystem20 (and the PDP-10 before) were 36 bit two's complement machines. You had to go back to the PDP-1 if you want one's complement in the DEC line. The CDCs and UNIVACs were the only ones that were still kicking around in my era. >> >>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. > >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 [-- Attachment #2: Type: text/html, Size: 2527 bytes --]