From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on inbox.vuxu.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=5.0 tests=DKIM_INVALID,DKIM_SIGNED, HTML_FONT_LOW_CONTRAST,HTML_MESSAGE,MAILING_LIST_MULTI, MIME_QP_LONG_LINE,RCVD_IN_DNSWL_NONE autolearn=ham autolearn_force=no version=3.4.4 Received: (qmail 19235 invoked from network); 25 Sep 2020 16:17:01 -0000 Received: from minnie.tuhs.org (45.79.103.53) by inbox.vuxu.org with ESMTPUTF8; 25 Sep 2020 16:17:01 -0000 Received: by minnie.tuhs.org (Postfix, from userid 112) id E81E59CEE0; Sat, 26 Sep 2020 02:16:55 +1000 (AEST) Received: from minnie.tuhs.org (localhost [127.0.0.1]) by minnie.tuhs.org (Postfix) with ESMTP id B949494552; Sat, 26 Sep 2020 02:16:22 +1000 (AEST) Authentication-Results: minnie.tuhs.org; dkim=fail reason="signature verification failed" (1024-bit key; secure) header.d=mxes.net header.i=@mxes.net header.b="jQX52wWk"; dkim-atps=neutral Received: by minnie.tuhs.org (Postfix, from userid 112) id 52BF194552; Sat, 26 Sep 2020 02:16:19 +1000 (AEST) X-Greylist: delayed 346 seconds by postgrey-1.36 at minnie.tuhs.org; Sat, 26 Sep 2020 02:16:17 AEST Received: from smtp-out-5.mxes.net (smtp-out-5.mxes.net [198.205.123.85]) by minnie.tuhs.org (Postfix) with ESMTPS id 9487493D65 for ; Sat, 26 Sep 2020 02:16:17 +1000 (AEST) Received: from Customer-MUA (mua.mxes.net [10.0.0.1]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.mxes.net (Postfix) with ESMTPSA id B0E617599E; Fri, 25 Sep 2020 12:10:27 -0400 (EDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=mxes.net; s=mta; t=1601050230; bh=+8gx2xwCBC8mJn3K35PNV31+j6ijfHcvwu8WbeytS1g=; h=From:To:Subject:Date:Message-Id:In-Reply-To:References:Reply-To: Mime-Version:Content-Type; b=jQX52wWkXrcSYQJPVh9RLxqnUS+OFFJQ/kOEN3FyRgH1rBjE2LmsXO2nkIulVBjP3 +NGAansat1i3PKfD2Tlr8b39PcM/EkvNDMzRuot0BT3T/2A2F95FB3c4vjIw8Ac3gL ViyWBOFc+tzEKCa0tehGA7bfgiFg5q/1opbj0YqA= From: "Ronald Natalie" To: "Warner Losh" , "Noel Chiappa" Date: Fri, 25 Sep 2020 16:10:23 +0000 Message-Id: In-Reply-To: References: <20200925152108.2AD1218C0C1@mercury.lcs.mit.edu> User-Agent: eM_Client/8.0.3385.0 Mime-Version: 1.0 Content-Type: multipart/alternative; boundary="------=_MB3A41BC16-6116-43E8-8240-905DBAE2DF28" X-Sent-To: Subject: Re: [TUHS] One's complement (was: reviving a bit of WWB) X-BeenThere: tuhs@minnie.tuhs.org X-Mailman-Version: 2.1.26 Precedence: list List-Id: The Unix Heritage Society mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Ronald Natalie Cc: The Eunuchs Hysterical Society Errors-To: tuhs-bounces@minnie.tuhs.org Sender: "TUHS" --------=_MB3A41BC16-6116-43E8-8240-905DBAE2DF28 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: quoted-printable The DECSystem20 (and the PDP-10 before) were 36 bit two's complement=20 machines. You had to go back to the PDP-1 if you want one's complement=20 in the DEC line. The CDCs and UNIVACs were the only ones that were=20 still kicking around in my era. >> >>Just to confirm, I pulled out my PDP-10 Hardware Reference Manual; Vol=20 >>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=20 >>binary >>arithmetic." Selah. > >Back in school, we had our machine organization course. When we learned=20 >about 1's complement, the professor said "I've used a lot of machines=20 >that had this. You will likely never see one with it. There are no=20 >operational machines on campus with that."It stuck with me. We had a=20 >TOPS-20 machine... the odd turn of phrase was due to a professor that=20 >had a board of unknown origin hanging on the wall that was a rumored to=20 >be a CDC or similar... ah, the mid 80s... Warner --------=_MB3A41BC16-6116-43E8-8240-905DBAE2DF28 Content-Type: text/html; charset=utf-8 Content-Transfer-Encoding: quoted-printable
The DECSystem20 (and= the PDP-10 before) were 36 bit two's complement machines.=C2=A0 You had to= go back to the PDP-1 if you want one's complement in the DEC line.=C2=A0= =C2=A0 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.

<= /div>
Back in school, we had our machine organization cour= se. When we learned about 1's complement, the professor said "I've used a l= ot 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...=C2=A0 the odd turn of phrase was due to a profess= or that had a board of unknown origin hanging on the wall that was a rumore= d to be a CDC or similar... ah, the mid 80s...
Warner
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