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[24.113.81.134]) by smtp.gmail.com with ESMTPSA id a2sm17345214pgn.20.2021.12.01.00.46.44 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Wed, 01 Dec 2021 00:46:44 -0800 (PST) Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (Mac OS X Mail 13.4 \(3608.120.23.2.7\)) From: Rich Morin In-Reply-To: <20211130192718.C0401210F4@orac.inputplus.co.uk> Date: Wed, 1 Dec 2021 00:46:41 -0800 Content-Transfer-Encoding: quoted-printable Message-Id: References: <202111282026.1ASKQ5X41437843@darkstar.fourwinds.com> <202111282115.1ASLFK1Q1438854@darkstar.fourwinds.com> <202111282147.1ASLlND41439656@darkstar.fourwinds.com> <20211129011244.GJ18441@mcvoy.com> <702642B0-311F-4464-B0EB-44166731EAFC@iitbombay.org> <20211130192718.C0401210F4@orac.inputplus.co.uk> To: TUHS main list X-Mailer: Apple Mail (2.3608.120.23.2.7) Subject: Re: [TUHS] A New History of Modern Computing - my thoughts 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: , Errors-To: tuhs-bounces@minnie.tuhs.org Sender: "TUHS" > On Nov 30, 2021, at 11:27, Ralph Corderoy = wrote: >=20 > ... The point of that bit of history is they were not chip designers, = but > knew electronics and programming. Wilson designed the ARM's = instruction > set and it was a delight to code: very orthogonal, and every = instruction > had four-bits of condition-flag test, e.g. Carry Set, and a bit to > indicate if this instruction should set the condition flags. Thus > several instructions in a row could test the condition flags set by an > instruction a few earlier and unaltered since; this cut the need for > quite a few branches. ... I wrote a fair amount of PDP-11 assembler, back in the early 70's (about = 10K LOC). I was particularly happy with a routine that moved a cell = between a pair of doubly-linked, circular linked lists (a "free" list = and a "busy" list). The routine only had to modify six pointers, which isn't a hard problem. = The cute part was that it was able to do so using (IIRC) only eight or = nine instructions. The PDP-11's auto-increment mode obviated the need = for separate index modification code. I had previously written a fair amount of code for a Varian 620i, which = had an AQX architecture. The 620i wasn't _hard_ to program, but it = _was_ a bit tedious. The PDP-11, by comparison, was a programmer's = delight. Which brings me to a historical notion: The DG Nova (https://en.wikipedia.org/wiki/Data_General_Nova) came out = in 1969, just a bit before the PDP-11 = (https://en.wikipedia.org/wiki/PDP-11). My impression, when I (later = on) looked at the Nova ISA, was that they had moved in the right = direction from the AQX approach, but not quite far enough. DEC, IMNSHO, = got it right. (ducking). -r