TUHS December 2021

tuhs@tuhs.org

66 participants
45 discussions

by Arnold Robbins

Hi All. Mainly for fun (sic), I decided to revive the Ratfor (Rational Fortran) preprocessor. Please see: https://github.com/arnoldrobbins/ratfor I started with the V6 code, then added the V7, V8 and V10 versions on top of it. Each one has its own branch so that you can look at the original code, if you wish. The man page and the paper from the V7 manual are also included. Starting with the Tenth Edition version, I set about to modernize the code and get it to compile and run on a modern-day system. (ANSI style declarations and function headers, modern include files, use of getopt, and most importantly, correct use of Yacc yyval and yylval variables.) You will need Berkely Yacc installed as byacc in order to build it. I have only touch-tested it, but so far it seems OK. 'make' runs in like 2 seconds, really quick. On my Ubuntu Linux systems, it compiles with no warnings. I hope to eventually add a test suite also, if I can steal some time. Before anyone asks, no, I don't think anybody today has any real use for it. This was simply "for fun", and because Ratfor has a soft spot in my heart. "Software Tools" was, for me, the most influential programming book that I ever read. I don't think there's a better book to convey the "zen" of Unix. Thanks, Arnold

3 years, 4 months

Re: [TUHS] Encoding an ISA: Random Logic vs. Control Stores

by Douglas McIlroy

My take on defining random logic random logic : hardware :: spaghetti code : software Doug

3 years, 5 months

Encoding an ISA: Random Logic vs. Control Stores

by pbirkel＠gmail.com

I believe that the PDP-11 ISA was defined at a time when DEC was still using random logic rather than a control store (which came pretty soon thereafter). Given a random logic design it's efficient to organize the ISA encoding to maximize its regularity. Probably also of some benefit to compilers in a memory-constrained environment? I'm not sure at what point in time we can say "lots of processors" had moved to a control store based implementation. Certainly the IBM System/360 was there in the mid-60's. HP was there by the late 60's. -----Original Message----- From: TUHS <tuhs-bounces(a)minnie.tuhs.org> On Behalf Of Larry McVoy Sent: Monday, November 29, 2021 10:18 PM To: Clem Cole <clemc(a)ccc.com> Cc: TUHS main list <tuhs(a)minnie.tuhs.org>; Eugene Miya <eugene(a)soe.ucsc.edu> Subject: Re: [TUHS] A New History of Modern Computing - my thoughts On Sun, Nov 28, 2021 at 05:12:44PM -0800, Larry McVoy wrote: > I remember Ken Witte (my TA for the PDP-11 class) trying to get me to > see how easy it was to read the octal. If I remember correctly (and I > probably don't, this was ~40 years ago), the instructions were divided > into fields, so instruction, operand, operand and it was all regular, > so you could see that this was some form of an add or whatever, it got > the values from these registers and put it in that register. I've looked it up and it is pretty much as Ken described. The weird thing is that there is no need to do it like the PDP-11 did it, you could use random numbers for each instruction and lots of processors did pretty much that. The PDP-11 didn't, it was very uniform to the point that Ken's ability to read octal made perfect sense. I was never that good but a little google and reading and I can see how he got there. ... --lm

3 years, 5 months

Encoding an ISA: Random Logic vs. Control Stores

by Paul Ruizendaal

For DEC memo’s on designing the PDP-11 see bitsavers: http://www.bitsavers.org/pdf/dec/pdp11/memos/ (thank you Bitsavers! I love that archive) Ad van de Goor (author of a few of the memo’s) was my MSc thesis professor. I recall him saying in the early 80’s that in his view the PDP-11 should have been an 18-bit machine; he reasoned that even in the late 60’s it was obvious that 16-bits of address space was not enough for the lifespan of the design. --- For those who want to experiment with FPGA’s and ancient ISA’s, here is my plain Verilog code for the TI 9995 chip, which has an instruction set that is highly reminiscent of the PDP-11: https://gitlab.com/pnru/cortex/-/tree/master The actual CPU code (TMS99095.v) is less than 1000 lines of code. Paul

3 years, 5 months

A New History of Modern Computing - my thoughts

by Jon Steinhart

Eugene Miya visited by last week and accidentally left his copy of the book here so I decided to read it before he came back to pick it up. My overall impression is that while it contained a lot of information, it wasn't presented in a manner that I found interesting. I don't know the intended target audience, but it's not me. A good part of it is that my interest is in the evolution of technology. I think that a more accurate title for the book would be "A New History of the Business of Modern Computing". The book was thorough in covering the number of each type of machine sold and how much money was made, but that's only of passing interest to me. Were it me I would have just summarized all that in a table and used the space to tell some engaging anecdotes. There were a number of things that I felt the book glossed over or missed completely. One is that I didn't think that they gave sufficient credit to the symbiosis between C and the PDP-11 instruction set and the degree to which the PDP-11 was enormously influential. Another is that I felt that the book didn't give computer graphics adequate treatment. I realize that it was primarily in the workstation market segment which was not as large as some of the other segments, but in my opinion the development of the technology was hugely important as it eventually became commodified and highly profitable. Probably due to my personal involvement I felt that the book missed some important steps along the path toward open source. In particular, it used the IPO of Red Hat as the seminal moment while not even mentioning the role of Cygnus. My opinion is that Cygnus was a huge icebreaker in the adoption of open source by the business world, and that the Red Hat IPO was just the culmination. I also didn't feel that there was any message or takeaways for readers. I didn't get any "based on all this I should go and do that" sort of feeling. If the purpose of the book was to present a dry history then it pretty much did it's job. Obviously the authors had to pick and choose what to write about and I would have made some different choices. But, not my book. Jon

3 years, 5 months

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TUHS December 2021