TUHS

tuhs@tuhs.org

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6501 discussions

by Doug McIlroy

I would like to revive Lorinda Cherry's "parts". Implicit in "revival" is dispelling the hundreds of warnings from gcc -Wpedantic -Wall -Wextra. Has anybody done this already? Doug

4 years, 3 months

2^n-bit operands (Was reviving a bit of WWB)

by M Douglas McIlroy

> Does anyone know why the computer industry wound up standardising on 8-bit bytes? I give the credit to the IBM Stretch, aka 7030, and the Harvest attachment they made for NSA. For autocorrelation on bit streams--a fundamental need in codebreaking--the hardware was bit-addressable. But that was overkill for other supercomputing needs, so there was coarse-grained addressability too. Address conversion among various operand sizes made power of two a natural, lest address conversion entail division. The Stretch project also coined the felicitous word "byte" for the operand size suitable for character sets of the era. With the 360 series, IBM fully committed to multiple operand sizes. DEC followed suit and C naturalized the idea into programmers' working vocabulary. The power-of-2 word length had the side effect of making the smallest reasonable size for floating-point be 32 bits. Someone on the Apollo project once noted that the 36-bit word on previous IBM equipment was just adequate for planning moon orbits; they'd have had to use double-precision if the 700-series machines had been 32-bit. And double-precision took 10 times as long. That observation turned out to be prescient: double has become the norm. Doug

4 years, 3 months

GBACA

by Mary Ann Horton

The topic of GBACA (Get Back At Corporate America), the video game for the BLIT/5620, has come up on a Facebook group. Does anyone happen to have any details about it, source code, author, screen shots, ...? Thanks, Mary Ann

4 years, 3 months

Re: [TUHS] for now [COFF] to follow up - why a byte is 8-bits

by Clem Cole

I will ask Warren's indulgence here - as this probably should be continued in COFF, which I have CC'ed but since was asked in TUHS I will answer On Wed, Feb 3, 2021 at 6:28 AM Peter Jeremy via TUHS <tuhs(a)minnie.tuhs.org> wrote: > I'm not sure that 16 (or any other 2^n) bits is that obvious up front. > Does anyone know why the computer industry wound up standardising on > 8-bit bytes? > Well, 'standardizing' is a little strong. Check out my QUORA answer: How many bits are there in a byte <https://www.quora.com/How-many-bits-are-there-in-a-byte/answer/Clem-Cole> and What is a bit? Why are 8 bits considered as 1 byte? Why not 7 bit or 9 bit? <https://www.quora.com/What-is-a-bit-Why-are-8-bits-considered-as-1-byte-Why…> for my details but the 8-bit part of the tail is here (cribbed from those posts): The Industry followed IBM with the S/360.The story of why a byte is 8- bits for the S/360 is one of my favorites since the number of bits in a byte is defined for each computer architecture. Simply put, Fred Brooks (who lead the IBM System 360 project) overruled the chief hardware designer, Gene Amdahl, and told him to make things power of two to make it easier on the SW writers. Amdahl famously thought it was a waste of hardware, but Brooks had the final authority. My friend Russ Robeleon, who was the lead HW guy on the 360/50 and later the ASP (*a.k.a.* project X) who was in the room as it were, tells his yarn this way: You need to remember that the 360 was designed to be IBM's first *ASCII machine*, (not EBCDIC as it ended up - a different story)[1] Amdahl was planning for a word size to be 24-bits and the byte size to be 7-bits for cost reasons. Fred kept throwing him out of his office and told him not to come back “until a byte and word are powers of two, as we just don’t know how to program it otherwise.” Brooks would eventually relent on the original pointer on the Systems 360 became 24-bits, as long as it was stored in a 32-bit “word”.[2] As a result, (and to answer your original question) a byte first widely became 8-bit with the IBM’s Systems 360. It should be noted, that it still took some time before an 8-bit byte occurred more widely and in almost all systems as we see it today. Many systems like the DEC PDP-6/10 systems used 5, 7-bit bytes packed into a 36-bit word (with a single bit leftover) for a long time. I believe that the real widespread use of the 8-bit byte did not really occur until the rise of the minis such as the PDP-11 and the DG Nova in the late 1960s/early 1970s and eventually the mid-1970s’ microprocessors such as 8080/Z80/6502. Clem [1] While IBM did lead the effort to create ASCII, and System 360 actually supported ASCII in hardware, but because the software was so late, IBM marketing decided not the switch from BCD and instead used EBCDIC (their own code). Most IBM software was released using that code for the System 360/370 over the years. It was not until IBM released their Series 1 <https://en.wikipedia.org/wiki/IBM_Series/1>minicomputer in the late 1970s that IBM finally supported an ASCII-based system as the natural code for the software, although it had a lot of support for EBCDIC as they were selling them to interface to their ‘Mainframe’ products. [2] Gordon Bell would later observe that those two choices (32-bit word and 8-bit byte) were what made the IBM System 360 architecture last in the market, as neither would have been ‘fixable’ later.

4 years, 3 months

Re: [TUHS] Fwd: Choice of Unix for 11/03 and 11/23+ Systems

by jnc＠mercury.lcs.mit.edu

> From: Greg A. Woods > There's a "v6net" directory in this repository. > ... > I wonder if it is from either of the two ports you mention. No; the NOSC system is an NCP system, not TCP; and this one has mbufs (which the BBN v6 one did not have), so it's _probably_ a Berkleyism of some sort (or did the BBN VAX code have mbuf's too; I don't recall - yes, it did: https://minnie.tuhs.org//cgi-bin/utree.pl?file=BBN-Vax-TCP see bbnnet/mbuf.c). It might also be totally new code which just chose to re-use that meme. I don't have time to look closely to see if I see any obvious descent. > Too many broken half-baked MUAs seem to still be widely used. I'm one of the offendors! Hey, this is a vintage computing list, so what's the problem with vintage mail readers? :-) Noel PS: I'm just about done collecting up the MIT PWB1 TCP system; I only have the Server FTP left to go. (Alas, it was a joint project between a student and a staffer, who left just at the end, so half the source in one's personal area, and the other half's in the other's. So I have to find all the pieces, and put them in the system's source area.) Once that's done, I'll get it to WKT to add to the repositoey. (Getting it to _actually run_ will take a while, and will happen later: I have to write a device driver for it, the code uses a rare, long-extinct board.)

4 years, 3 months

Re: [TUHS] Fwd: Choice of Unix for 11/03 and 11/23+ Systems

by Paul Ruizendaal

> V6, as distributed, had no networking at all. There are two V6 systems with > networking in TUHS: > > https://minnie.tuhs.org//cgi-bin/utree.pl?file=SRI-NOSC <https://minnie.tuhs.org//cgi-bin/utree.pl?file=SRI-NOSC> > https://minnie.tuhs.org//cgi-bin/utree.pl?file=BBN-V6 <https://minnie.tuhs.org//cgi-bin/utree.pl?file=BBN-V6> > > The first is an 'NCP' Unix (unless unless you have an ARPANet); the second is > a fairly early TCP/IP from BBN (ditto, out of the box; although one could write > an Ethernet driver for it). I’ve also done a port of the BBN VAX stack to V6 (running on a TI990 clone), using a serial PPP interface to connect. Experimental, but may have the OP's interest: https://www.jslite.net/cgi-bin/9995/dir?ci=tip > There's also a fairly nice Internet-capable V6 (well, PWB1, actually) from MIT > which I keep meaning to upload; it includes SMTP, FTP, etc, etc. I also have > visions of porting an ARP I wrote to it, and bringing up an Ethernet driver > for the DEQNA/DELQA, but I've yet to get to any of that. I’d love to have a look at that and compare and contrast the approaches. I’m finding that BBN’s original design, with a separate kernel thread for the network stack, is elegant but difficult to tune: too much priority and it crowds out user processes, too little and the slow PPP line is not kept busy. I think I’m beginning to understand why CSRG (and later also BBN) moved to the interrupt driven structure of 4.2BSD: perhaps it was also difficult to tune for a VAX with ethernet.

4 years, 3 months

Re: [TUHS] Fwd: Choice of Unix for 11/03 and 11/23+ Systems

by jnc＠mercury.lcs.mit.edu

> From: Paul Riley > In the bootable images archive, there's the "Unknown V6" RL02 > image. I've tried that on SimH configured as an 11/23+ with 256kB of RAM > and it seems to work fine. Sorry, where's this archive? Somewhere in: https://www.tuhs.org/Archive/Distributions/Research/ I assume? From the description, that might be from the 'Shoppa disks'; didn't realize that was a /23 on those. > I would assume that Ethernet boards are available, but not supported on > V6. V6, as distributed, had no networking at all. There are two V6 systems with networking in TUHS: https://minnie.tuhs.org//cgi-bin/utree.pl?file=SRI-NOSC https://minnie.tuhs.org//cgi-bin/utree.pl?file=BBN-V6 The first is an 'NCP' Unix (unless unless you have an ARPANet); the second is a fairly early TCP/IP from BBN (ditto, out of the box; although one could write an Ethernet driver for it). There's also a fairly nice Internet-capable V6 (well, PWB1, actually) from MIT which I keep meaning to upload; it includes SMTP, FTP, etc, etc. I also have visions of porting an ARP I wrote to it, and bringing up an Ethernet driver for the DEQNA/DELQA, but I've yet to get to any of that. > it's hard to glean that wisdom from reading the manual. Yeah, DEC manuals went through a phase-change around about the time of the /23. Old DEC manuals are wonderful; stuffed to the gills with deep technical details. Suitable for engineers... Later, they turned into manuals for 'ordinary people' - 'plug cable C1 into plug P1'. Semi-useless; although one can often glean a few useful morsels if you trawl through the entire thing. That's why I've been doing PDP-11 pages on the CHWiki which attempt to cover a lot of technical detail, in a high technical content/size way. If you need something that's not there, let me know, and I'll get to adding it. Noel

4 years, 3 months

reboot(2) system call

by Warner Losh

I've done some research for a friend about when the reboot() system call was added, and how it related to the sync, sync, sync dance. https://bsdimp.blogspot.com/2020/07/when-unix-learned-to-reboot2.html may be of interest. Please do let me know if I've gotten something wrong... Warner

4 years, 3 months

QED archive READMEs updated

by Arnold Robbins

Hello All. I have updated various READMEs in the QED archive I set up a while back: https://github.com/arnoldrobbins/qed-archive. Now included is a link to Leah's blog, mention that the SDS files came from Al Kossow, and Doug's link to the Multics QED cheat sheet. Thanks, Arnold

4 years, 3 months

[TUHS} Qed vs ed

by M Douglas McIlroy

> fairly early in PDP-11 development ed gained three features: & in the > rhs of substitutions plus k and t commands. (I'm not sure about & .... Oh, and backreferencing, which took regular expressions way up the complexity hierarchy--into NP-complete territory were it not for the limit of 9 backreferenced substrings. (Proof hint: reduce the knapsack problem to an ed regex.) Also g and s were generalized to allow escaped newlines. I was indeed wrong about &. It was in v1. Doug

4 years, 3 months

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