test-drb April 1999

test-drb@ccmp.vtda.org

170 participants
1190 discussions

How scarce (valuable) is core for the PDP-8?

by CLASSICCMP＠trailing-edge.COM

>I'm serious. I really have wanted to build something like this. In terms >of size, the problem isn't the wiring, it's the redundant circuitry. Most of the DEC core planes use a fair number of special-purpose transistor arrays (often specially matched) for drivers as well as pulse transformers and delay lines. If you look back at alt.sys.pdp8 archives (or its mailing-list twin, PDP8-LOVERS) you'll find some suggestions for part substitutions and/or rebuild directions. I believe that at least one of the electronics rags in the Lasnerian mid-70's (Radio Electronics? Popular Electronics?) published an article on using surplus core arrays that were readily available at the time, but the article was remarkably detail-free when it came to the actual details of driving and sensing. There were at least a few implementations of S-100 core memory in the mid-70's, and one of them was a S-100 to Unibus translator of sorts. (Not to be confused with the IMSAI S-100/Unibus shared memory module, which is in several of my IMSAI price lists from 1977/1978 but which I believe to be vaporware.) -- Tim Shoppa Email: shoppa(a)trailing-edge.com Trailing Edge Technology WWW: http://www.trailing-edge.com/ 7328 Bradley Blvd Voice: 301-767-5917 Bethesda, MD, USA 20817 Fax: 301-767-5927

25 years, 8 months

heads up; OSI Challenger 1P

by allisonp＠world.std.com

<Well, I don't know the Electrical Codes across the Pond exactly (I have a <fair idea of the UK regulations...), but I think I read somewhere that <you can't have a 220V outlet for equipment less than a certain wattage <(1.4kW comes to mind). Seems a very silly regulation, but then a lot of <regulations are. Meaningless. I have a pigtail at the box with a 3terminal twist and lock (hubble) wired for 220. It's there as general use for heating in the garage or welding equipment if I had it. I've used it for testing motors (1/4HP) that were clearly under 1.4kw. The codes are aimed at providing reasonable power. Here a 15A/115v is the nominal and 115V/20A is a max but 220/208 at any current the mains can be wired for is common. It would be foolish to sell 220V/1500W hair dryers here as the nominal mains are expected to handle that kind of load. Allison

25 years, 8 months

UNIBUS Terminators

by healyzh＠aracnet.com

25 years, 8 months

DEC BC11A-15 Cable

by healyzh＠aracnet.com

25 years, 8 months

z80 timing... 6502 timing

by edick＠idcomm.com

While your comments are valid observations, I submit, however, that we're coming at this from two different viewpoints. I wish to address the question "Which processor is faster, 6502 or Z-80?" while you want a general comparison of processors. Unfortunately, answering one question doesn't address the other. Dick -----Original Message----- From: Bill Yakowenko <yakowenk(a)cs.unc.edu> To: Discussion re-collecting of classic computers <classiccmp(a)u.washington.edu> Date: Wednesday, April 21, 1999 12:26 AM Subject: Re: z80 timing... 6502 timing >On 19 Apr 1999, Richard Erlacher <edick(a)idcomm.com> wrote: >] It's true that may be more interesting when you have different vehicles, but >] if you're trying to determine which of two is faster, don't you focus on >] those two? Having lots of variations in the hardware only tends to muddy >] the water. > >Obviously, some of us care about vehicles other than those two. >Doesn't muddy _my_ waters one bit. :-P > >I, for one, am interested in processor capabilities independent >of video/disk/etc gorp. Roman numerals isn't going to be a >thorough comparison, but it's better than nothing, and small >enough to be fun. If this is still going on in a month or two, >maybe I'll write an entry myself. As it is now, my schedule >barely allows me to keep up with all the stuff you guys are >writing! > > > >And then, later the same day, regarding my suggestion about >noting the relative ages of processors when comparing their >results, he wrote: >] It's pretty hard to imagine how a limitation like your suggestion would >] apply. Newer processors addressed weaknesses in the older ones. One of >] those was ease of programming. In some cases, e.g. the 6809, the processor >] was designed with a regular instruction set and lots of addressing modes so >] as to make generating code easy. It didn't necessarily make it faster. I >] don't know how elegant such code will ultimately turn out to be. > >If you want to get a handle on which processors were really >better than others performance-wise, you look at the best they >can do on some specific problems. Granted, the results may >not be easy to interpret because of varying environmental >characteristics. Welcome to Earth. Nothing is simple here. > >Obviously, if the 6809 loses to some older processor, its >adherents can still claim ease-of-coding as a benefit. But it >would still be interesting to know if it could regularly get >whomped by a measly, pathetic, sad-excuse-for-a-processor like >the 6502. :-) :-) :-) :-) > >My suggestion was not meant as any sort of limitation, just my >take on what kind of result would be interesting; one way of >interpreting the results. If an older processor doesn't do as >well as the newer one, well, we expected that. But if an older >one outperforms a newer one, there is something worth exploring >there, a lesson to be learned about an improvement really wasn't. > > Bill. > >

25 years, 8 months

DEC Options Module List

by CLASSICCMP＠trailing-edge.COM

>> In the case of DEC parts, having a dumpster-dived copy of the "Option/Module >> Hardware List" stamped "DEC Confidential" all over it helps a little >> bit :-). >The holy grail of DEC dumpster divers everywhere. >Unfortunately, mine stayed at DEC when I left. I was a good boy when >I left.

25 years, 8 months

Program Challenge (was Re: z80 timing... 6502 timing)

by ethan_dicks＠yahoo.com

--- Sean 'Captain Napalm' Conner <spc(a)armigeron.com> wrote: > > Problem: Convert a binary value to Roman, using ASCII characters (or > > the native character set if applicable) into a string > > with a termination character (if ASCII, use the NUL (0) > > character). > > > Sorry, I goofed. The longer string is 16 characters long: > > 'MMMDCCCLXXXVIII' plus termination character. In terms of how to represent numbers like 1999 (MIM or MCMXCIX), the rule I learned as a kid was that it was not proper to subtract any numeral >from any other numeral willy-nilly. Only certain combinations were allowed and you had to just memorize them. Here's some links to some pages with something to say about Roman Numerals http://www.cod.edu/people/faculty/lawrence/romans00.htm http://www.col-ed.org/cur/math/math41.txt http://www.mcn.net/~jimloy/roman0.html http://raven.bu.edu/~grozdits/student/roman_num.html ... and we now return you to your regularly scheduled Off Topic discussions... -ethan _________________________________________________________ Do You Yahoo!? Get your free @yahoo.com address at http://mail.yahoo.com

25 years, 8 months

Program Challenge (was Re: z80 timing... 6502 timing)

by mbg＠world.std.com

>And again, more questions: >If I'm right at Megans description, she just include the next lower >digit when it comes to these subtraction rules, and your Algo seams >to be weak at the same point. Let me give an example: >49 would be normaly coded as IL (always remember, it was kind of a >system to reduce writing as much as possible - there are even examples >where the number 248 is written CIIL) while Megan seams to code it as >XXXXIX - basicly wrong - or did I miss something ? I'm not realy >what one can call a DEC-Geek. My code would produce XLIX, not XXXXIX... I guess I'm unclear as to whether any numeral can be used to reduce the value of a higher, subsequent numeral. Using your explanation, 1999 would be MIM, instead of the more standard (as I have seen it) MCMXCIX. Also, what's to stop someone from writing it in a form employing the vinculum: __ III >So do we only have to supporte the one-less rule, or the rule >of one subtraction numeral - or the full possibility with the >goal to reduce writing to a max ? So long as someone can clearly explain the rules to what can be subtracted from what, I'll implement it... (kind of like requiring a spec). Without it, I can only go on what I can find documented in the encyclopedia... Megan Gentry Former RT-11 Developer +--------------------------------+-------------------------------------+ | Megan Gentry, EMT/B, PP-ASEL | Internet (work): gentry!zk3.dec.com | | Unix Support Engineering Group | (home): mbg!world.std.com | | Compaq Computer Corporation | addresses need '@' in place of '!' | | 110 Spitbrook Rd. ZK03-2/T43 | URL: http://world.std.com/~mbg/ | | Nashua, NH 03062 | "pdp-11 programmer - some assembler | | (603) 884 1055 | required." - mbg | +--------------------------------+-------------------------------------+

25 years, 8 months

Saving *BIG* Old Iron...

by gentry＠zk3.dec.com

It looks like everything is coming together... We have a team assembled (compiled?) to decommission and move a set of KS10 decsystem-10 36-bit machines and the move happens this weekend! I was in attendance earlier today as the machines were shut down for the final time where they have been for quite a few years. I got a picture of the final systat screen, and they stopped timesharing... We then got busy unloading and shutting down all the disk drives. I then shut down the individual boxes and power controllers for the system cabinets and isolated the cabling (they had LOTS of terminal cables). I then raised all the stabilizing feet and used a tie-wrap to attach the panel keys inside the cabinet. I then closed and latched the front doors. I also did the same for the tape drive cabinets. They're all rolling free and ready to go. On friday, we'll be pre-staging all the disk drives, and on saturday we load-out to trucks. I'll be taking more pictures as we go along... Megan Gentry Former RT-11 Developer +--------------------------------+-------------------------------------+ | Megan Gentry, EMT/B, PP-ASEL | Internet (work): gentry(a)zk3.dec.com | | Unix Support Engineering Group | (home): mbg(a)world.std.com | | Compaq Computer Corporation | | | 110 Spitbrook Rd. ZK03-2/T43 | URL: http://world.std.com/~mbg/ | | Nashua, NH 03062 | "pdp-11 programmer - some assembler | | (603) 884 1055 | required." - mbg | +--------------------------------+-------------------------------------+

25 years, 8 months

Counting keystrokes

by Watzman＠ibm.net

Believe it or not, the most common use of keeping keystrokes was for employee evaluation. I remember weekly postings of graphs of "keystrokes/hour" in data entry and word processing departments, with a weekly "prize" [nominal value] for the "best" data entry operator of the week. This and similar productivity measurement measures were not uncommon.

25 years, 8 months

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test-drb April 1999