test-drb

test-drb@ccmp.vtda.org

101090 discussions

Some things make me want to toss my cookies ...

by CLASSICCMP＠trailing-edge.com

>> http://www.bccc.com/nancy/memorydress.html > >Core memory in oscilliscopes? Where did she get that idea? She also talks about medical equipment, which causes me to believe that most of the core memory she gets comes out of pulse height analyzers >from the late 60's to the mid 70's. These look a lot like oscilliscopes to the untrained idea (they have a CRT, lots of knobs, BNC jacks, etc.) -- 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

26 years, 1 month

More 3rd Party DEC boards

by healyzh＠aracnet.com

Hmmm, this is really odd, I found some more boards that I don't seem to have inventoried today. Anyone have any ideas on these? Versatec PDP-11 Matrix control This is a dual height board, but I'm pretty sure it's for a UNIBUS system, thanks to the wierd connector sticking out the side of it for another board. DILOG DQ342 Quad Height, has a 34 and a 10-pin connector SCD-RQD11/EC Quad Height, 4 20-pin connectors, 1 34-pin, and 1 10-pin. 3 LED's 2 green, 1 red. I think it's a Sigma ESDI controller, based on doing a DejaNews search, it also looks like it _might_ be basically a rebadged WQESD controller, since the one article talks about WOMBAT. Is this correct, and can I just use my WQESD manual for it? Plessey P/N 705920-100A Quad Height, RAM board Zane | Zane H. Healy | UNIX Systems Adminstrator | | healyzh(a)aracnet.com (primary) | Linux Enthusiast | | healyzh(a)holonet.net (alternate) | Classic Computer Collector | +----------------------------------+----------------------------+ | Empire of the Petal Throne and Traveller Role Playing, | | and Zane's Computer Museum. | | http://www.dragonfire.net/~healyzh/ |

26 years, 1 month

The "FIRST PC" and personal timelines (Was: And what were the 80s

by CLASSICCMP＠trailing-edge.COM

>Or what would your definition of Micocomputer be? I suppose we have to >establish that first. graphic monitor and floppy drive, with hard drive >optional, would seem a good start. By those standards, even an IBM 5150 (aka "IBM PC") wasn't even a microcomputer. I think that sort of definition is way too narrow. Then a gain, I despise most any kind of exclusionary definition. But that doesn't leave one with much in the way of definitions left, does it? :-). I *do* like the web page that Sam pointed out ( http://www.blinkenlights.com/pc.shtml ). I may not agree with the final positive, but I do agree with all the previous negatives :-). And that Arkay CT-560 looks pretty nifty! Tim.

26 years, 1 month

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

by jdykstra＠nortelnetworks.com

I have several jars of ferrite cores made by IBM sometime in the late 1950's. I don't know exactly what size they are, but they can be hand-wired without a stereo microscope. I know, because I built a plane of 1x64x64 when I was in high school in 1971. (I was very determined to build my own computer.) The project was abandoned when I went away for college, which was probably a good thing, because my analog design skills were not up to creating the drive and sense circuitry. As I recall, I used something like #60 enameled wire. One of the challenges was stripping the insulation off the ends of the wires without damaging the copper. If anyone is seriously intending to build a demo core memory system, I'd be glad to provide a couple of hundred cores. I'd recommend something like a 16x16 array, unless you're looking for a project to make a 20-to-life sentence go faster. ---- John Dykstra jdykstra(a)nortelnetworks.com Principal Software Architect voice: ESN 454-1604 Enterprise Solutions fax: ESN 667-8549

26 years, 1 month

More pdp-8 Docs Added

by kstumpf＠unusual.on.ca

Thank you man. Lots of work followed by lots of benefit. Yours in good faith. ---------------------------------------------------------------------------- ------------------------------- Kevin Stumpf * Unusual systems * www.unusual.on.ca +1.519.744.2900 * EST/EDT GMT - 5 Collector - Commercial Mainframes & Minicomputers from the 50s, 60s, & 70s and control panels and consoles. Author & Publisher - A Guide to Collecting Computers & Computer Collectibles * ISBN 0-9684244-0-6 .

26 years, 1 month

PC Jr

by fpp＠concentric.net

On Mon, 26 Apr 1999, PG Manney wrote: > I recently acquired a PCjr with a bunch of software. Machine's very clean. > > I'm not really that interested in playing with this beast. Should I sit on > it as an investment? Is it worth anything now? Dnyone interested? It is a relative situation. Value is what is it worth to you or the buyer. A few points about the computer. There are not that many floating around for sale. It was a flop for IBM but it also was IBM's entr?e into the "Home computer" market. This gives it some weight. The PC and its siblings had supplanted the PC jr and nailed the lid on the coffin, but I would hang on to it, it will not become valuable for a while but it is a "place marker" in the history of computers. What did its introduction mean to the industry? Altair- first viable personal computer, Apple I computer, first of the longest lived manufacturer. (Yes IBM has been around longer but not as a PC maker) 1st Sony PC, the design and implementation of the 3.5" diskette, Tandy the first mass market machine not only sold in computer stores, Commodore Pet, First computer to make the cover of a national general circulation magazine (Popular Science) and from a calculator company no less; using calculator keys for the keyboard. The Commodore also set a standard for selling computers to computer dealers in their original selling agreements. Vector Graphics, first computer company founded and run by a woman. Osborne, the computer made by the guru of computer hobbyists and Kaypro, first generally accepted computer for the average business person. Want to know the value of a computer? Is it a piece of hardware or a point of computer history, did it change the way things were done? Good luck.

26 years, 1 month

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

by Philip.Belben＠pgen.com

I wrote > BTW Siemens make some torroidal cores down to 1mm thick ferrite, slightly larger > in other materials. RS Components stock some - http://rswww.com/ and go in > through the catalogue: "Electronics", "Transformers/Inductors/Ferrites", > "Ferrites", "Torroids" (sic). There are even data sheets but I didn't manage to > download them. So it seems that RS and I made the same spelling mistake. I think "Toroid" and "Toroidal" are the correct spellings... P.

26 years, 1 month

XXDP+ 2.5

by healyzh＠aracnet.com

NOTE: my problems are at the end of this message, got carried away to the extent someone might find this to have some useful info :^) I'm trying to run some tests on my /44 and have been having loads of fun with my lack of doc's on XXDP+. Note, for people in the same boat, I'd recommend Pete Turnbull's notes http://www.dunnington.u-net.com/public/XXDP.ps Though the best help I've found is having the doc's on the hardware I've tried to test. The /44 Tech Manual says to run 1-11 of the following tests in order (NOTE: I added the XXDP+ column). MAINDEC Operating Title XXDP+ 2.5 Diagnostic Sequence --------------- ------- ------------------------------- ----------- CKK FA <xy> 1 11/44 Diagnostic ROM* CKK AA <xy> 2 11/44 CPU/EIS KKAAB0.BIC CKK AB <xy> 3 11/44 Traps KKABD1.BIC CKK TA <xy> 4 11/44 Mem. Mgt. Prt A KKTAB1.BIC CKK TB <xy> 5 11/44 Mem. Mgt. Prt B KKTBD0.BIN CZM 9B <xy> 6 M9312/11/44 UBI Boot ZM9BE0.BIN CKK UA <xy> 7 11/44 UBI Map KKUAE0.BIN CKK KA <xy> 8 11/44 KK11-B Cache KKKAC0.BIC CZM SD <xy> 9 MSL-M/L Memory ZMSDD0.BIN MS11-L/M/P Memory Diagnostic ZMSPC0.BIC CZD LD <xy> 10 DL11-w/MFM SLU ZDLDI0.BIN CKK AC <xy> 11 11/44 Power Fail KKACC0.BIC CKF PA <xy> 12 FP11-F Part A KFPAD0.BIC CKF PB <xy> 13 FP11-F Part B KFPBC0.BIC CKF PC <xy> 14 FP11-F Part C KFPCD0.BIC CZK EE <xy> 15 PDP-11 CIS Instr. Exerciser ZKEEC0.BIC CZK UA <xy> 16 UNIBUS Systems Exerciser Diag. ZKUAE0.BIN CZK UB <xy> 17 UNIBUS Exerciser Module ZKUBC0.BIN *Included with the M7098 UBI module. CKFPA ||\/| || |Indicates a series of diagnostics: A= part 1, B=part 2, C=part 3, etc. || | (this is what the PDP-11/44 Tech Manual claims, I'm not convinced || | that it was followed) || Indicates a specific device tested by the diagnostic: || "FP" = Floating Point Diagnostic || "RK" = RK05 (disk diagnostic) |"K" indicates a specific diagnostic for the PDP-11/44 system. "C" indicates a PDP-11 diagnositic (not used on diagnostic disk pack or magnetic tape). <xy> = x = Revision Character (alpha) y = Patch Number (0-9) My single biggest problem seems to be stopping a diagnostic once I've started it. So far I've been resorting to stopping the CPU and rebooting, but one would think that there must be a better way, and that I've missed it. My second problem is the first test, I can't find a KKFA*.* test. Is there another test I can run on the diagnostic ROM? #3 is #3, but I think this is proper behavior CKKABD0 11/44 TRAPS NO FLOATING POINT OPTION PRESENT NO CIS OPTION PRESENT CONSOLE 17777707 023252 >>> Problem #4 isn't that big a deal, the "M9312/11/44 UBI Boot" diagnostic complains that the DD and DL ROMS are in as DL and DD, while it wants DD and DL. #5 may or may not be a problem with the cache (real problem is my not knowing how to interpret it). CKKKAC0 11-44 KK11B CACHE RMI REGISTER (G5179) NOT USED-SKIP HI ORDER BIT ADDRESS TEST UNIBUS EXERCISER NOT USED-DMA TESTS NOT PERFORMED END OF PASS # 1 END OF PASS # 2 END OF PASS # 3 <etc,etc,etc> I solved #6 by finding and substituting the ZMSPC0 memory test for ZMSDD0. Opps, guess I didn't try step 11, and 12-14 can't be done at the moment as the FP11 isn't installed, and I don't have a CIS for #15, 16&17 both complained. Zane | Zane H. Healy | UNIX Systems Adminstrator | | healyzh(a)aracnet.com (primary) | Linux Enthusiast | | healyzh(a)holonet.net (alternate) | Classic Computer Collector | +----------------------------------+----------------------------+ | Empire of the Petal Throne and Traveller Role Playing, | | and Zane's Computer Museum. | | http://www.dragonfire.net/~healyzh/ |

26 years, 1 month

Mystery UNIBUS Boards?

by jrbrady＠mindspring.com

Greetings All, Can you help identify these UNIBUS boards? They were found in a BA11-K expansion box in a VAX 11/750. The VAX was used to run the equipment in an MRI trailer. I didn't remove the system and don't know to what type of equipment it was originally connected. 1) Full size genuine DEC hex board, no "M" number on spine. "DIGITAL" and "BSWU-T" etched on front. Two stickers, marked "835084" and "4522 117 2760". 93 TTL chips, 18 PAL chips, 5 DIP switch blocks, two 50-pin connectors for ribbon cables. On rear side, "4522 111 91963" etched and a sticker with "PR32.4B" and "MB6024ET". 2) Plessey Peripheral Systems quad board. Marked with "P/N 703680- 100E" on front, "703679-001 REVB" on rear. 7 chips with stickers "218 101C, 102C, 103C, 104C, 105C, 100 UK30, UK2A". 62 TTL chips. 1 50-pin connector with cable to what appears to be an interface board (#3 below). 3) 8" by 10" board connected to Plessey board above. 2 50-pin connec- tors on top. Etched with "C-FTR", "FDD-FTR", "FTR-FTR". 12 26LS31 & 32 chips, 10 TTL. Instead of card-edge fingers, has 2 3-level male 3x32 pin AMP3485 connectors which plug into corresponding female receptacles in BA11-K box (one group of hex slots replaced with these). Any help identifying these boards is appreciated. Doubt I'll ever use them, but nice to know what they might be! BTW - Posted this inquiry to comp.sys.dec & alt.sys.pdp11 awhile back so it may look familiar. Thanks, Jason Brady jrbrady(a)mindspring.com Lynnwood, WA

26 years, 1 month

TRW Swaps/CompuCrawls

by jpl15＠netcom.com

Well.. amplifying what Sellam has written... the very first SoCal CompuCrawl is in the history books. It takes up about two sentences. ;} The Gathering was small but intense... we had big fun, tho. I gave away some lonely equipment to a Good Home, and we played with some of my Geek Toys. I got a cool t-shirt with 'GEEK' emblazoned boldly for all to see and snicker at. Marvin behaved himself for the most part, and law enforcement assistance was thankfully not required at any time during the entire soiree. Since there were several of Us who apparently had to cancel at the last minute, I am strongly considering having another next month, instead of next quarter (september) as I had originally planned. Also, various folks mentioned to me that logistics and/or transportation issues affected their participation. Anyone needing a ride to-from should contact me directly and we'll sort it out. So again: if there is any interest between now and the next SoCal TRW swap meet, on the last Saturday of May (the 29th? 30th?) from local and visiting Listmembers, I will again hold a Vintage Computer open house after the TRW swapmeet and post-swap Brunch, and thereafter, quarterly. Mark Your Calendars! (Use spray paint this time) Cheers John

26 years, 1 month

PC Jr

by manney＠hmcltd.net

I recently acquired a PCjr with a bunch of software. Machine's very clean. I'm not really that interested in playing with this beast. Should I sit on it as an investment? Is it worth anything now? Dnyone interested? Thanks P Manney Is it illegal to yell "Movie!" in a fire station? Thousands of discounted photo items at http://www.hmcltd.net/pgphoto

26 years, 1 month

More pdp-8 Docs Added

by mcquiggi＠sfu.ca

Hi All: Ten more scanned documents added to the http://highgate.comm.sfu.ca/pdp8 web site tonight. Kevin --- Kevin McQuiggin VE7ZD mcquiggi(a)sfu.ca

26 years, 1 month

Old computer books? Oh, we shred them!

by guerney＠uq.net.au

Every two years at this time the University of Queensland Alumni Association holds a large sale of old books donated by individuals plus library discards. I've found some good collectables there in the past, such as old manuals, but this time (today) it took me five minutes to just find where the computer books were - instead of a full trestle table top as in previous years, there was just 4 inches of space reserved for them - maybe 20 books in a hall of many many thousands. I found the lady in charge and asked what had happened to them? She said "we kept any computer books dated in the 50's or 60's (I didn't find any), and anything fairly recent, but all donations from the 70's and 80's went out." I asked "Did you send them to one of the charities to sell at their bookfests?". Her response "oh no, they just go straight to the shredder! - we can't get rid of them otherwise." And sadly, I suspect she was correct. Besides the odd character like me looking for manuals for long gone models, most of the stuff that went out for sale was rubbish to 99.99+% of people and stayed on the table at the end of the day. But I sure wish she had at least given me the chance to look through that stuff before it hit the shredder. The good news was that I found amongst the "sets" (encyclopedias etc) a full set (I think, 22 volumes anyway) of the Time-Life series Understanding Computers. Lots of good computer history and pictures - but I would be interested if anyone has any criticism of the facts presented in any of the articles in that series - they seem authoritative enough, but then some of the people on this list know more than the usual sources that Time-Life writers would have used. Phil in Brisbane, Australia.

26 years, 1 month

PC question

by mbg＠world.std.com

Yesterday, at the KS10 move, I came away with two IBM PCs, but I don't know enough about them to know if they are the AT or XT models... they both have a 5.25" floppy and a hard drive, and both have color monitors. They are both desktop boxes... the monitors were sitting on top of them. So, how do I tell... 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 | +--------------------------------+-------------------------------------+

26 years, 1 month

HP1000M

by jlwest＠tseinc.com

Hum.... Thanks for the tip on the seller! My M series is sick, so I was just getting ready to fire off an email asking what cards were in the memory backplane.... with a record like that, I don't think I'll bother (now if it was a 7900A drive, I'd forge ahead anyways <grin>)! Jay West

26 years, 1 month

Power connectors

by Philip.Belben＠pgen.com

>> Hey, Sallam, couldn't this power thing be a good addition for >> VCF 3.0? A speach about how to operate Eq. from a different >> country (and power system) in an acceptable and safe fashion ? >> Maybe if Philip and me (possible with a thirs, US guy) team up >> to give an outline of the different circumstances to remember >> when using foreign (old) computers ? There might be some need. > > Yes, I think this would make for a great workshop. I expect more people > to start trading computers across the world and this will make for a very > relevant discussion. I think it's an excellent idea. In fact I have long thought a computer-buff's guide to power electrics (the mains) would be worth writing. But I doubt I'll manage VCF 3 this year. A holiday in CA is not something I do every year, alas... Philip.

26 years, 1 month

Powerlines

by danburrows＠mindspring.com

>2. Phase. > >As I understand it the usual practice in the US is take _either_ a phase and >earth (neutral) _or_ two phases of the HV supply and feed a single phase >transformer from this. The LV side of the transformer is (say) 240V with a >centre tap. The centre tap is earthed and provides the neutral connection, the >outer two taps are then both hot at 120V, 180 degrees apart. This is true _even >if_ the primary (HV winding) is connected between two phases of the HV 3-phase >system. Close but not quite right. For single phase installations the power company supplies 2 hots and neutral. This is a center tapped secondary and the neutral is earthed at the service entrance. The primary of this transformer is fed from only 1 high voltage phase. >In the UK the usual practice is to connect all 3 phases of the HV (almost >invariably 11kV phase to phase) to a delta-star 3-phase transformer. The >secondary, the star-connected winding provides 3 phases and neutral. Neutral is >earthed at the transformer. Protective earth can be provided by _either_ a >separate wire from the main earth at the transformer _or_ an earthing electrode >at each customer's site _or_ the neutral is earthed at a large number of points >on the system and the customer's protective earth is bonded to neutral at the >point of entry of the supply. In all cases the customer sees 240V line to >neutral; if he gets more than one line (hot) connection, they will be 120 >degrees apart. The delta-star is the same but with 120 phase to neutral and 208 phase to phase. In the UK it is the same but 240 phase to neutral and 416 phase to phase. You can also commonly find 480 3 phase delta- star 277 phase to neutral. This is then used for lighting (277 florescent is common) and large loads like air conditioning. In these installations the customer has to provide their own transformer to 208/120. >In remote locations, only 2 phases of the 11kV system are taken to the site. >Small loads get a single phase 11kV/250V transformer with one end of the LV >earthed; larger loads get a single phase 11kV/500V transformer with a centre tap >earthed. Some farm equipment (I am told - I have never seen this) is rated for >480V single phase. I don't think this is avail. in the US. > >It is very unusual for a domestic installation to get more than one phase and >neutral. But 3-phase can be done - the supply company don't mind putting it in >if they think you'll buy a lot of electricity! They will here also and I checked into getting it here but I am a few miles >from the closest point that 3 phase is available for distribution. I would either have to guarentee a large $ per month usage or pay them to add the additional lines. Over $10,000 was mentioned. Dan

26 years, 1 month

Some things make me want to toss my cookies ...

by cmcmanis＠freegate.com

http://www.bccc.com/nancy/memorydress.html

26 years, 1 month

DEC documentation RUMOR????

by clintw＠colorado.cirrus.com

Hi all, I read a web page somewhere that indicated DEC put in the public domain all the documentation they no longer publish. Is this true? Can anyone point me back to the original web page? Thanks, clint

26 years, 1 month

Cores, light bulb goes on ...

by allisonp＠world.std.com

<Ok after spending much of the weekend trying to get my core driver working <and feeling really good about having all the parts I needed in my spares <box, I realized I had built half of an h-bridge. Since I had already <designed a really nice MOSFET based h-bridge that could switch 10 - 15 amp <for my robots I slapped my head and went "Doh!" ;) that will do. <Anyway, so I wired up my #2 nut with sense wire to the h-bridge and start <slapping current back and forth through my nuts. :-) Seriously though when <viewed on 'scope it looks something like: < < +--+ < | | <Ch1 -+ +----+ +----- < | | < +--+ < +--+ <Ch2 -+ +----+ +----- < +--+ Transformer action prior to saturation. <UNTIL you get to about 7.5 amps or so, and then it looks like: No you know what nuts dont work... < +--+ < | | <Ch1 -+ +----+ +----- < | | < +--+ < +--+ <Ch2 ---+ +----+ +----- < +--+ < <So I stared at it a bit and the little bulb went on between my ears. < <The first pulse "writes" a zero to the core, if the core is either already <magnetized with a zero, or has nothing in it, then the sense line sees the <deta-B (change in magnetic field) and a current is induced in the wire. <When the second pulse comes along it "writes" a one into the core, same <effect on the sense wire. The clever part comes when your "write" a zero t <a core that has a one already written to it. Core is one of the few DESTRCUTIVE READ memories. You have to try and flip it to see if it flips, if it does you had a (one or zero) and if didn't you have a (zero or one). Designing circuits the transformer and the "bistable" properties makes for interesting logic. <In this case the current in the wire induces its standard magnetic field, <but that field is _cancelled_ by the field already in the core, thus for a <period of time the sense line sees no change in magnetic flux, and so no <current is induced. Then however the core switches to 0 and the sense wire <sees that change in flux and out comes the induced pulse now delayed from <the initial point by a time controlled by how long it took to saturate the <core and switch it. Yep. Watching that spring snap in interesting on a scope. Those nuts are slow too! Try a bunch of other materials now that your set up... <The gap between the pulse start and the sense pulse is used to tell whethe <or not the core had a 1 in it. Now in the DEC design what happens after th <read pulse (which is really a "write zeros" pulse, is they take the data <they just read and re write with the write ones pulse. However this time <since the sense lines aren't needed to figure out what the cores had in <them, they use them for "inhibit" currents. They used seperate wires (four wire cores) in some cases as it was easier that all that switching. <-------------------------- <Cool stuff, now it raises some new questions: < 1) Do you want your pulses to be long enough to switch the < core exactly, or longer? (eg does writing a zero just cancel < a one or does it cancel the one and write a zero in its place?) I forget. < 2) Why not just gate the write one current pulse? That would save < on the inhibit current stuff. well you have to know what your writing back and to do that you have to read it first. Hence the common write after read cycle on many machines >from the era of core. < 3) What properties of a material make it easier to switch at lower < currents? I don't want to build a core plane with nuts if I need < 8 amps to switch them. Good magnetic conductors that hold their magnetizm. Some steels, ferrites, cobalt alloys, alnico, a few rare earths. Try some of those ferrite beads used for bypassing in RF work. Allison

26 years, 1 month

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

by allisonp＠world.std.com

<OK, how about it. Put a ring of compasses around the wire with needles str <enough magnetised that they will stay pointing N-S around the ring regardle <the Earth's field. < <Can you then flip them with a current? A very good visual demonstration of <core works! Yep, That would be good to watch but that's really a demo of the fields around conductors (imporant building block). Allison

26 years, 1 month

HP 1000 on eBay : auctioned by unresponsive bidder

by ss＠allegro.com

Hi, I was about to send this just to ccauction list, but I realized that some ClassicCmp readers might not read ccauction ... and they might have an interest. In a rather misleading title: "antique Altair-like HP-1000 M-series computer" dschambe(a)uiuc.edu is selling a partially gutted HP 1000 computer. http://cgi.ebay.com/aw-cgi/eBayISAPI.dll?ViewItem&item=95719221 This seller has consistently refused to respond to my email about two items that I got for low bids on prior auctions...so I have never been able to finalize the purchase. If anyone from this list does bid on the HP 1000, and wins, please encourage this guy to honor his *existing* committments before sending him money! thanks! sieler(a)allegro.com

26 years, 1 month

Cores, light bulb goes on ...

by cmcmanis＠freegate.com

Core memory, the saga continues. Ok after spending much of the weekend trying to get my core driver working, and feeling really good about having all the parts I needed in my spares box, I realized I had built half of an h-bridge. Since I had already designed a really nice MOSFET based h-bridge that could switch 10 - 15 amps for my robots I slapped my head and went "Doh!" Anyway, so I wired up my #2 nut with sense wire to the h-bridge and start slapping current back and forth through my nuts. :-) Seriously though when viewed on 'scope it looks something like: +--+ | | Ch1 -+ +----+ +----- | | +--+ +--+ Ch2 -+ +----+ +----- +--+ UNTIL you get to about 7.5 amps or so, and then it looks like: +--+ | | Ch1 -+ +----+ +----- | | +--+ +--+ Ch2 ---+ +----+ +----- +--+ So I stared at it a bit and the little bulb went on between my ears. The first pulse "writes" a zero to the core, if the core is either already magnetized with a zero, or has nothing in it, then the sense line sees the deta-B (change in magnetic field) and a current is induced in the wire. When the second pulse comes along it "writes" a one into the core, same effect on the sense wire. The clever part comes when your "write" a zero to a core that has a one already written to it. In this case the current in the wire induces its standard magnetic field, but that field is _cancelled_ by the field already in the core, thus for a period of time the sense line sees no change in magnetic flux, and so no current is induced. Then however the core switches to 0 and the sense wire sees that change in flux and out comes the induced pulse now delayed from the initial point by a time controlled by how long it took to saturate the core and switch it. The gap between the pulse start and the sense pulse is used to tell whether or not the core had a 1 in it. Now in the DEC design what happens after the read pulse (which is really a "write zeros" pulse, is they take the data they just read and re write with the write ones pulse. However this time since the sense lines aren't needed to figure out what the cores had in them, they use them for "inhibit" currents. Remembering that the cores were all written to zero by the 'read' when the write 'ones' pulse comes along you don't want it writing cores that you want to keep zero (they had zero before). So a current that is in opposite direction of the write current is sent down the sense lines where zeros should be kept. The magnetic field generated by these "inhibit" currents cancel the magnetic field created by the "write ones" current and thus prevents those cores with a 'zero' in them from being written to '1'. -------------------------- Cool stuff, now it raises some new questions: 1) Do you want your pulses to be long enough to switch the core exactly, or longer? (eg does writing a zero just cancel a one or does it cancel the one and write a zero in its place?) 2) Why not just gate the write one current pulse? That would save on the inhibit current stuff. 3) What properties of a material make it easier to switch at lower currents? I don't want to build a core plane with nuts if I need 8 amps to switch them. --Chuck McManis

26 years, 1 month

FW: VAX 6500 in Minneapolis.

by kstumpf＠unusual.on.ca

PLEASE REPLY DIRECTLY TO THE AUTHOR OF THE ORIGINAL MESSAGE. >Reply-To: <kenp(a)trlab.com> >From: "Ken Peck" <kenp(a)trlab.com> >To: <kstumpf(a)unusual.on.ca> >Subject: Computer Hardware for Museum >Date: Mon, 26 Apr 1999 16:28:02 -0400 >X-MSMail-Priority: Normal >Importance: Normal >X-MimeOLE: Produced By Microsoft MimeOLE V4.72.3110.3 >X-UIDL: e7780be67b36c9d8688e16fdc0bca942 > >Kevin, > >There is a Vax 6500 in Minneapolis, >Minnesota that will be de-installed in June. I thought perhaps there might >be some interest in the historical value of it for some collector or museum. >If you or someone you know might be interested, please let contact me. > >Regards, > >Ken Peck >Total Renal Laboratories, Inc. >1991 Industrial Dr. >Deland, Fl. 32724 >800.604.5227 > > > ---------------------------------------------------------------------------- ------------------------------- Kevin Stumpf * Unusual systems * www.unusual.on.ca +1.519.744.2900 * EST/EDT GMT - 5 Collector - Commercial Mainframes & Minicomputers from the 50s, 60s, & 70s and control panels and consoles. Author & Publisher - A Guide to Collecting Computers & Computer Collectibles * ISBN 0-9684244-0-6 .

26 years, 1 month

The "FIRST PC" and personal timelines (Was: And what were the80s

by edick＠idcomm.com

The previous comment should have made it obvious it was NOT within the reach of the "average" American. First of all, it was over a month's pay for the average American, it was equivalent to six months' groceries for a family of four, and you could get a refrigerator or a washer, neither of which were routine discretionary expenditures for the "average" American of that time. That was during and immediately after the Korean war, when a 4-bedroom house on a 1/4-acre lot cost $4600. That same house, now, in California would cost you $4600 a month to rent. People's attitudes about what's important enough to spend your money on have changed considerably. $300 was not an expenditure an "average" American would consider lightly in 1952. That was the year I came to this country. There was an election between Adlai E. Stevenson (Democrat) and Dwight D. Eisenhower (Republican). It was BEFORE the first test of a hydrogen bomb. People weren't crazy then as they are now . . . and all the loose nuts hadn't yet learned to run to California. Dick -----Original Message----- From: Sellam Ismail <dastar(a)ncal.verio.com> To: Discussion re-collecting of classic computers <classiccmp(a)u.washington.edu> Date: Thursday, April 22, 1999 10:16 PM Subject: Re: The "FIRST PC" and personal timelines (Was: And what were the80s >On Thu, 22 Apr 1999, Richard Erlacher wrote: > >> No, what's relevant isn't the technology and its state of maturity, but the >> comparison of the relative value of the numbers. Today, it's just assumed >> that if you buy an item for $300 and it subsequently breaks, you shrug your >> shoulders and throw it away. Back in the '50's, not many people were silly >> enough to do that. > >So what? $300, even back in the 50s, was still realistically within the >price range of the average American. A multi-million dollar mainframe was >not. $300 vs $$$millions is a significant difference. > >Sellam Alternate e-mail: dastar(a)siconic.com >--------------------------------------------------------------------------- --- >Don't rub the lamp if you don't want the genie to come out. > > Coming this October 2-3: Vintage Computer Festival 3.0! > See http://www.vintage.org/vcf for details! > [Last web site update: 04/03/99] >

26 years, 1 month

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