test-drb

test-drb@ccmp.vtda.org

101090 discussions

by kstumpf＠unusual.on.ca

I am selling an 11/45 out of the rack for US$150. Please contact me for details if you are interested. ---------------------------------------------------------------------------- ------------------------------- 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, 6 months

Northstar Horizon

by edick＠idcomm.com

This isn't exactly what you're discussing, but . . . I've got, in my hand an S-100 board, not fully populated, silkscreened "North Star Computers, Inc. Z-80A Processor Board Z80-A2" I'll send this jewel via USPS Priority mail, as is, to the first person whose $3.20 I get in the mail to cover mailing. Dick -----Original Message----- From: Tony Duell <ard(a)p850ug1.demon.co.uk> To: Discussion re-collecting of classic computers <classiccmp(a)u.washington.edu> Date: Wednesday, June 02, 1999 2:53 PM Subject: Re: Northstar Horizon >> > > And I need to bring up a terminal, or configure >> > > something to function as a terminal. >> > A PC with comms software is nice as you can use the logging feature to >> > save scribbling notes as you bring it up. >> >> Except that it adds a few minor additional interfacing variables. If I >> get NOTHING, would I assume that it's a problem with the N*, or could it >> be configuring of HYPERTERMINAL? I think that the FIRST step, that of >> getting a character or two through, would best be accomplished with the >> simplest terminal available. I have a lunchbox machine; I should see if >> it has a working serial port, and try something like PROCOMM. > >Having recomended a complex piece of test gear in another message, here >I'll recomend something simple that I wouldn't like to be without - a >'Christmas tree' type RS232 tester. One of those little in-line adapters >with red/green LEDs on the major lines (TxD, RxD, RTS, CTS, DSR, DTR, >CD). > >If I am ever bringing up an unknown machine which uses a serial terminal, >I stick that on the port in line to whatever terminal I am using. Then I >can tell if the machine is trying to send something as the TxD (or RxD, >as appropriate) LED will flicker. Of course it'll also tell me if an >unknown port is a DTE or DCE, and will help sort out handshaking problems. > >Although I have a lot of other RS232 test gear (several breakout boxes, a >comms monitor, etc), I use this more than all the others put together. > >If you want to make one, all it consists of are those 2-colour LEDs (red >and green diode in antiparallel) with 2 wires in series with a 3k >resistor (3k3 would also work) between the above mentioned signals and >Signal Ground. But they're pretty cheap to buy ready-made. > >-tony >

26 years, 6 months

SD Sales/Systems EXPANDORAM

by edick＠idcomm.com

Wouldn't you know it, I've got a non-functional pair of Expandorams as well. the first is an Expandoram, the second is an Expandoram II. Both were fully functional when I packed them in their wrappings some fifteen years ago, and boxed them but I think the switches may have gotten fiddled-with in the course of cleaning them. The memory IC's check out. Does anyone have doc's on the required settings? thanx Dick

26 years, 6 months

How your collection storage space is used?

by mbg＠world.std.com

>Please ponder this question. >We either collect mainframes, minicomputers, or microcomputers. In the >mix there is hardware, software, documentation, spares, and related >material such as magazines, books, novelties. There might also be the >original boxes. >What percentage of your space is taken up by the hardware and how much >by everything else? What is the ratio of actual computers to all the >other stuff that goes along with them? Please tell me the catagory(s) of >computer(s) you collect (mainframe, etc.), and what your percentages >are. I mostly collect DEC hardware -- easy since I worked at DEC for 20 years and was able to partake of DEC salvage when it was open. In recent months I've started collecting in different directions, mostly just things which strike my fancy. I can't say that I am trying to collect any specific type of machines (other than the DEC ones), just random examples of computers. As for how much room it takes up... let me put it this way, my S.O. and I live in one condo, my computers live in another (and I visit to feed and water and work on them). The largest of the machines are the pdp-11/10, pdp-11/34a and the pdp-8s. They may only take up 24sqft of floor space, but they are 6' high, so they take up a fair amount of volume. I must say, however, that most of the stuff which takes up room are all the boxes of manuals, handbooks, disks, spare boards, cables, etc. that I have to keep them working. So, I would say in my collection, about 30% to 40% of the space is taken up by the actual machine collection, the rest is taken up by the support stuff. 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, 6 months

AT&T 3B2 300

by lemay＠cs.umn.edu

Does anyone here have experience with AT&T 3B2 300 hardware/software? I apparently have a pile of doc and software which is in complete disarray. The software is all on 5.25" DSDD diskettes, and i'm not even sure if i have what i need to format and reinstall an operating system. Does anyone know what type of hard drives these computers support, or know if the floppy drive can be upgraded to high density? I have two base systems, one has either been cannibalized, or merely every screw has been removed, since everything from the power supply to the floppy drive is floating free in the case ;) The other unit appears to be in much better shape. The student chapter of ACM at the university here had these, so you can imagine what sacrelige may have been comitted... -Lawrence LeMay lemay(a)cs.umn.edu

26 years, 6 months

MV3100s

by Innfogra＠aol.com

One of my dealers sent the following to his mail list. I thought this group might be interested. Please contact him directly. Paxton We have an enduser client that is selling the following MV3100 systems. They need an offer as soon as possible. (FOB Michigan) QTY Part# Description 9 dv-470m-b9 MicroVax 3100/80 4 dv-31eta-a MicroVax 3100 3 dv-31btb-a MicroVax 3100 2 dv-31ct1-a MicroVax 3100 2 dv-31rta-a9 MicroVax 3100/95 10 vs48k-aa VaxStation 4000 VLC *systems are complete, but we have no description of memory configurations, hard drive sizes, etc., (licenses may become available, but if you are interested, bid if no licenses are included) ** part numbers and descriptions provided by enduser - you may want to verify Contact: Bob Frischkorn Network Management Corp. 440-285-8400 or email netman(a)netman2000.com

26 years, 6 months

HP-125 System FS.

by kstumpf＠unusual.on.ca

If you are interested please contact Jim: clmoving(a)jetnet.ab.ca or phone 780.594.7566 Jim told me it is working, has printer and disk drive, and THE ORIGINAL BOXES. 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, 6 months

DEC pdp11/70 console docs

by ebrens＠dds.nl

Hello, recently I acquired a pdp11/70 in semi-working condition, but alas, documentation for the console board was not included :/ Anybody here who is in the lucky position to make me some scans/copies, or maybe someone knows where I can find 'em in digital (scanned) form ? Thanks in advance, Erikb.

26 years, 6 months

IMSAI IMP-48

by allisonp＠world.std.com

Peroidically I do this in hopes of... I have an IMSAI IMP48 SBC. It was given to me 20 years ago but not the docs. I'd be interested in finding docs for it even if only a copy. Allison

26 years, 6 months

How your collection storage space is used?

by allisonp＠world.std.com

<> Please ponder this question. <> <> We either collect mainframes, minicomputers, or microcomputers. In the mi <> there is hardware, software, documentation, spares, and related material <> such as magazines, books, novelties. There might also be the original <> boxes. <> <> What percentage of your space is taken up by the hardware and how much <> by everything else? What is the ratio of actual computers to all the othe <> stuff that goes along with them? Please tell me the catagory(s) of comput <> you collect (mainframe, etc.), and what your percentages are. < <This is not an easy question to answer... I collect SBCs, S100 and small dec systems (Robin, Pro, DECmate, pdp-8, PDP-11, VAX) and the occasional odd (unusual) PC. How much space, 150sqft room is cubed out. Also three steel racks plus floor space(roughly 500cuft) in the garage. By actual count some 50 (may have missed a few) systems total. All but a small few are operable or in use. The key is that I collect a mix and if they have anyhting in common they were the systems I drooled over when to were far to expensive to have bought them all new. Allison

26 years, 6 months

VECTOR GRAPHICS 64K DRAM Card - switch settings?

by edick＠idcomm.com

Well . . . it seems to work, now that I've fiddled with the broken jumper wire. The wire was broken but the insulation wasn't, and it was done so neatly, I couldn't initially believe it was a user-installed jumper wire. Now that that's done, I can put it in the "works" box . . . Thanks for the help. Dick -----Original Message----- From: Marvin <marvin(a)rain.org> To: Discussion re-collecting of classic computers <classiccmp(a)u.washington.edu> Date: Thursday, June 03, 1999 7:04 PM Subject: Re: VECTOR GRAPHICS 64K DRAM Card - switch settings? > Richard Erlacher wrote: > > Would anyone be able to help me with this VECTOR GRAPHICS 64K DRAM BOARD's > switch settings? The signals seem to be OK, but no data propagates from > the thing. I'm not anxious to count through the combinations of > settings. According to the schematics for the Rev-3 board, S1 is the Bank Select with positions 0 - 7 (or probably labeled 1 - 8) corresponding to D0 - D7. D0 - D7 go through 74175 Quad D latches and come out on the Not Q outputs. These are then all anded together (U41 - 74ls30) to output the Bank Select signal. Hmmm, interesting, it looks like the inputs are left floating when the switch is open, and I have a hard time believing that with LS type circuitry. There is a note indicating: Jumper Memory Enabled 1 to 3 0000h - FFFFh 5 to 3 0000h - DFFFh 4 to 3 0000h - BFFFh, E000h - FFFFh 2 to 3 0000h - BFFFh

26 years, 6 months

VECTOR GRAPHICS 64K DRAM Card - switch settings?

by edick＠idcomm.com

Would anyone be able to help me with this VECTOR GRAPHICS 64K DRAM BOARD's switch settings? The signals seem to be OK, but no data propagates from the thing. I'm not anxious to count through the combinations of settings. thanx Dick

26 years, 6 months

and here's another one . . .a JADE Memory Bank!

by edick＠idcomm.com

Well . . . I'm going through all these piles of S-100 boards, see, and I put the working ones in that box over there, see, and then I put the ones that don't over in this box. I've got this Jade Memory Bank and don't seem to have the doc's for it any more either. . . and it has THREE switch blocks along with over a dozen jumpers . . . it even seems to have an IC missing. . . . Does anyone of you guys have any detailed doc's on this one? Dick -----Original Message----- From: Erik Brens <ebrens(a)dds.nl> To: Discussion re-collecting of classic computers <classiccmp(a)u.washington.edu> Date: Thursday, June 03, 1999 6:26 PM Subject: Re: DEC pdp11/70 console docs > >> documentation for the console board was not included :/ > > ^^ >Hello again, > >by "console board", I actually meant the front console panel (the thing >with the switches on it). > >> Thanks in advance, >> Erikb. >> >

26 years, 6 months

DEC treasure trove available

by manney＠hmcltd.net

I have a friend (Yes, Virginia, I have two friends) who's been a DEC repairman for many years. He now wants to get rid of the accumulated a lot of stuff in his barn, and has asked me to help get rid of it. I'm not sure I have the time to make a complete catalogue of all his stuff. Anyway, I know squat about big iron, and therefore don't know what's valuable to people. Please, therefore, email me with your wants -- anything from, "I'll take anything" to "keep an eye out for this widget". I have no idea what he wants for all of this, bit I doubt he's out to gouge. manney(a)hmcltd.net pgphoto(a)ragemail.com P Manney "Y1K caused the Dark Ages." Thousands of discounted photo items at http://www.hmcltd.net/pgphoto -----Original Message----- From: Colan Mitchell <cdrmool(a)interlog.com> To: Discussion re-collecting of classic computers <classiccmp(a)u.washington.edu> Date: Wednesday, May 26, 1999 4:37 PM Subject: confidential info on old harddrives. > >If this is a ? thats been dealt with before I joined the list my >apologies. > I repeatedly come across personal and confidential information on >discarded computers. I sit and shake my head in shock. Lawyers seem to >be the worst. I have considered contacting the original owners and >educating them about practicing safe hex but, especially in the case of >lawyers and women, don't want to have them freak out and think I'm being >weird and calling the police. On the other hand I feel that I should do >something. In the end I just format the drives and forget about it. > Has anyone experienced contacting an original owner? What was the >response. This is something that I've not read about in the media as Y2K >and Hackers get all the press but I suspect this is a bigger potential >problem. > > >Colan > > > > >

26 years, 6 months

Mattel handheld Football 2 (1978)

by I8ABoogar＠aol.com

I have Two in great condition Steve

26 years, 6 months

More Bringing up a CPM

by stephen.j.gabaly＠lmco.com

> > Hi > > Let me see, that is 384 machine pin sockets in 2102's alone. > > Do you have a special discount that you might share? > Sorry to butt in, but I have a suggestion. I use collet pin carries, these are metal carriers with machined pins attached to them. You solder them on the board, remove the carrier, then you have 16 nicely placed machined pins free standing. This allows much easier inspection of the final solder joint since you don't have a plastic dip case in the way, I buy them by the 1000 at about 5 cents each (14 pin carriers, but you can get them any size) and that satifies all my socket needs. If I need 16 pin,20 pin or 40 pin (rare) sockets I simply remove the pins from a couple carriers and manually solder them. Also works well for transistors, caps, resistors or what have you. steve

26 years, 6 months

How your collection storage space is used?

by steverob＠hotoffice.com

> > What percentage of your space is taken up by the hardware and how much > by everything else? What is the ratio of actual computers to all the other > stuff that goes along with them? Please tell me the catagory(s) of computer(s) > you collect (mainframe, etc.), and what your percentages are. > > Thank you very much. > ------------------------------------------------------------------------ ---- . Kevin, I collect both micros and minis. I'd estimate that a microcomputer constitutes about 40% of the bulk. The documentation, software, and other pieces would account for the remaining 60%. For a mini, the computer with necessary peripherals (drives, etc...) probably account for about 80% of the bulk. Documentation, backup media, and other stuff taking the remaining 20%. Often times, the "other stuff" can be kept on top of the mini without impairing it's function. That generally doesn't work with a micro. Of course, I don't have the original shipping containers, pallets or packing material for a mini. That would skew the numbers a LOT! :-) Steve Robertson - <steverob(a)hotoffice.com>

26 years, 6 months

confidential info on old harddrives.

by cdrmool＠interlog.com

If this is a ? thats been dealt with before I joined the list my apologies. I repeatedly come across personal and confidential information on discarded computers. I sit and shake my head in shock. Lawyers seem to be the worst. I have considered contacting the original owners and educating them about practicing safe hex but, especially in the case of lawyers and women, don't want to have them freak out and think I'm being weird and calling the police. On the other hand I feel that I should do something. In the end I just format the drives and forget about it. Has anyone experienced contacting an original owner? What was the response. This is something that I've not read about in the media as Y2K and Hackers get all the press but I suspect this is a bigger potential problem. Colan

26 years, 6 months

Lobotomizing HyperTerminal >> Alternative

by roblwill＠usaor.net

Has anyone ever tried ProComm? It's a DOS terminal emulator that I use on an old Zenith SupersPORT 8088. Here's the different terminal that it can emulate: VT-100 TVI 920 TVI 950 VT-52 LS ADM5 HEATH 19 ANSI-BBS ADDS VP WYSE 100 IBM 3101 It's a pretty useful program, and doesn't take up too much space. I have it on all of my old laptops. ///--->>> -Jason Willgruber (roblwill(a)usaor.net) ICQ#: 1730318 <http://members.tripod.com/general_1>

26 years, 6 months

OMTI Series-10 bridge controller to SA-1000 series HD

by edick＠idcomm.com

I find myself without the necessary doc's to rewrite the BIOS for a system using a small in capacity but 8" in size HDD. Would any of you kind and resourceful souls have the necessary data on hand to help me out with this task? Thanx Dick

26 years, 6 months

More Bringing up a CPM

by edick＠idcomm.com

The point about the "best piece of equipment" is perhaps the thing I like best about using a logic analyzer for a difficult problem. It's such a pain to set up, it forces you to think through the analysis before making any measurements . . . or assumptions. Another nice feature is that you can rearrange the displayed waveforms without rearranging the probes. If you choose to see a signal set differently than you previously did, you don't necessarily have to redefine your trigger equations or any such fun. Dick -----Original Message----- From: Tony Duell <ard(a)p850ug1.demon.co.uk> To: Discussion re-collecting of classic computers <classiccmp(a)u.washington.edu> Date: Wednesday, June 02, 1999 5:29 PM Subject: Re: Re[6]: More Bringing up a CPM >> On the subject of LA/scope/logic probe/voltmeter. I personally >> consider a LA as the shot gun approach. It will often find >> problems when one has no idea where to look. The only problem > >I can't agree with that. OK, so a logic analyser will monitor a lot of >points at once, so you can test unrelated sections in the hope of finding >the fault. But when you've got 64 or 128 or whatever traces, you still >have to think about the fault. > >> is that someone with an oscilloscope can often have the >> machine repaired by the time one gets the leads connected > >I've found that a small logic analyser (say about 3-4 channels), >intellegently used, is very useful. It doesn't take long to connect it >up. And it will tell you a lot about the circuit you're investigating. > >> I rarely use a logic probe because I don't have one. I >> can use an oscilloscope just as well with the additional >> features that an oscilloscope can provide when needed. >> It is like a logic probe with more added. > >You _need_ a LogicDart :-) > >> Still the best overall trouble shooting tool I have is >> an analog voltmeter. I can move quicker with one of these > >I agree. I use my old analogue meter a lot more than a digital one. It's >a lot quicker to read an analogue meter for one thing. > >> than many can with other tools. As far as I'm concerned, >> DVM's are only good for setting power supply voltages. > >Oh, they are also useful for setting voltage references on analogue >subsystems. And checking the exact setting of a variable resistor (when >you want to change it to (say) 3 time the value as an inital point in a >modification). > >> I have one ( an accurate 5 digit unit ) but the analog meter >> is still the first thing I reach for. > >There are 4 instruments that get most of the use on my bench. In order : > >An analogue VOM. >The LogicDart >A good bench PSU (30V, 10A). Useful for powering up subsystems independantly >A cheap handheld 'scope, audio band only. Useful for checking for PSU >ripple, looking at motor drive waveforms, SMPSU waveforms, etc. > > >> I find that most don't know how to trouble shoot. The >> sequence is simple but many still don't get it: >> >> 1. Observe symptoms >> 2. Make predictions >> 3. validate predictions >> 4. If predictions do not pan out add this >> to the observed symptoms and go back to step 2 or 1. >> 5. Repair bad part. >> >> I find that most don't understand the importance of steps >> 2 and 3. They try to go from 1 to 5 and usually it doesn't >> work. Step 2 does require that you understand what to >> expect from each kind of failure. > >My method is related to that... > >1) Look for silly faults (cables fallen out, etc). Check fuses, etc >2) Unless there's a very good reason, power up and observe the fault >3) Do some standard checks. Check PSU rails, master clock, etc >4) Think of possible causes for the observed symptoms >5) Do tests (either execute commands or make measurements) to check out >each possible cause. >6) If no possible cause is the cause of the fault, you've missed one of >the possible causes. >7) You now know the bad part. > >The best piece of 'test equipment' you can have is a brain. _Always_ >think about the fault before trying to cure it. Often I make some intial >measurements and then sit and think for maybe an hour before doing >anything else. > >-tony >

26 years, 6 months

More Bringing up a CPM

by edick＠idcomm.com

please see embedded comments below: Dick -----Original Message----- From: Dwight Elvey <elvey(a)hal.com> To: Discussion re-collecting of classic computers <classiccmp(a)u.washington.edu> Date: Wednesday, June 02, 1999 5:18 PM Subject: Re[2]: More Bringing up a CPM >"Richard Erlacher" <edick(a)idcomm.com> wrote: >--snip-- >> The logic analyzer won't hide significant information about the logic and >> timing. If you sample at twice the frequency of the fastest harmonic you >> want to observe, you won't miss a thing. > > It is not just frequency issues. Levels can be a problem as >well. I've seen circuits with mixed HC, LS, 4000 and other. >You set the input for one and the other is wrong. Also, >your 2X has to be twice the frequency of the response >of the IC circuit and not just twice the clock speed. >Also, the 2X sampling rule is only true for repetitive >signals. This is a basic sampling law thing. >100 Mhz isn't really fast enough to truly see what is >going on in even an old 8080 processor board. Glitch >catching helps but can still hide correct operation. > Where I currently work, we are completely out of the >ball park were current day LA's are of much use but >that is another problem. We still have them and can, >under limited conditions, use them. > I can assure you that you won't run into much CMOS circuitry in the old IMSAI and Altair stuff. You're right, of course, if your instrument can't be programmed to handle different thresholds then you could be persuaded you see something you really don't, or perhaps be swindled out of seeing what's really there. I remember looking at some new CMOS circuitry about 15 years ago when the high-speed CMOS stuff was still new. It appeared, for all the world, as though the outputs preceded the inputs of a series of gates by quite a difference. I had set my 2467 display to the lower threshold of a cmos schmidt trigger and displayed a couple of other signals with respect to that, including the clock which triggered a sequence. It appeared that the 'Q' of a flipflop preceded the clock by quite a margin, perhaps 3-4 ns. We quickly concluded that a sufficiently long chain would easily allow us to read tomorrow's stock quotations today, thereby making us all rich. - - - it didn't work that way! The way I get around the random sampling error in observing a crystal driven microprocessor circuit is that I use a little PLL to multiply the clock on the board by some constant, say 4, 10, 16 or some such, and sample at that rate as opposed to what the LA wants to use. That makes similarly long pulses look similarly long as opposed to suffering from the temporal distortion introduced by the asynchronism between the LA sampling clock and the circuit on the board under observation. Of course, like a 'scope or signal generator, you have to know how to drive them, just as you must know how to interpret the results. The LA often points up where to hook the 'scope. If it cuts my search through 60-70 signals down to half a dozen, it's made itself worthwhile. I find the LA really handy for MCU-driven cirtuitry, since I can use the LA to take a picture and then spiff it up and print it in the O&M manual. What's more, with easily simulated FPLD's, it's really handy to compare the simulation with what the LA sees. It's often quite heartening to see what you thought you ought to see after working on one of those babies for a couple of weeks. In any case, I've troubleshot dozens of DRAM circuits with either the little front-end sampling mux or a real LA, and have found them to be invaluable in finding component failures, incorrenct jumpering, wrong delay lines, etc. What's more, if I didn't make the mistake, I can prove it. If I did, I can prove I fixed it. That's worth quite a bit of setup. As far as frequency is concerned, the only problem I've encountered which doesn't quickly show up on a LA display is metastability. As fast as things run these days, and with the widespread use of fully synchronous circuitry, almost everything goes into a device through a two-bit shift register stage to mitigate metastability. I find that if I sample at twice or quadruple the clock which drives the pipeline registers, I can catch everything I need. Those old circuits like the IMSAI and ALTAIR CPU circuits relied quite a bit on circuits' propagation delays to build events. Races were common, and that's why folks used to tack 20-400 pf caps all over those boards in hopes of making them work better. Like I wrote before, setup and interpretation is slow, painstaking, and laborious. It's often wrong the first time. Unless you have half-a-dozen similar boards to work on, it's hardly worth the trouble.

26 years, 6 months

Mattel handheld Football 2 (1978)

by ethan_dicks＠yahoo.com

--- I8ABoogar(a)aol.com wrote: > I have Two in great condition What's the microprocessor? I used to have one of those when I was a kid. My father might still have it in the attic (I know he has a box of those sorts of things, but I don't know the exact contents, and he's several states away). I recently saw a Mattel Baseball game at a Hamfest, but I've never seen the Football for sale. -ethan _________________________________________________________ Do You Yahoo!? Get your free @yahoo.com address at http://mail.yahoo.com

26 years, 6 months

More Bringing up a CPM

by allisonp＠world.std.com

<I can't agree with that. OK, so a logic analyser will monitor a lot of <points at once, so you can test unrelated sections in the hope of finding <the fault. But when you've got 64 or 128 or whatever traces, you still <have to think about the fault. I'd also point out that if the LA in not connected into the system correctly it can by virtue of ground loops and other things like the leads actually induce problems. Seen that occur to people. same for scopes too! I'm not saying they are bad but for some stuff you can end up looking for the forest between the trees. the best example was a multibus design bring up another engineer was doing and the board didn't do what was predicted and of course it was surrounded with scopes LAs and even probes... the problem... 8086 asm MOV AH,Ah ( was supposed to move the immediate value x0A to register A high byte!) Them trees can hurt when the land of you. Allison

26 years, 6 months

More Bringing up a CPM

by allisonp＠world.std.com

<A Z80 will give useful patterns executing continual 00 (NOP, so the <address bus cycles through all of memory) or FF (RST 38, so the stack <builds down to fill all off memory). Both should provide useful patterns <on DRAM control lines. Indeed they do. If you want to force a pattern, the inbound bus buffer can have pins lifted (if socketed). There are pleny of tricks before getting out the "big guns". For the cannons for ants set I do have a S100 Bus debugger that was use use the phrase purpose built. It's a Logic analyser that has 4 leads floating and 32 (address and datain plus data out) and a riot of controls so that it's possible to do a bus level logic analysis and it has 16kx40bits of 2167 55ns ram to take a extended picture of things. I built it to deal with the quad processor system as there were a lot of signals running. <Like Allison I used to work almost entirely with a logic probe and a VOM <(and a brain, which is the most important 'instrument' of all :-)). I had <a good logic analyser, which saved me a lot of time on occasions, but it <wasn't that convenient to use. I have a 16 channel LA and two good scopes but often as not if I poke and think as Dwight sugggested I rarely need to drag them out and set them up. The most common use for the LA is craking "black box" devices and chips. <I rarely use a 'scope for computer (digital) repairs. It's essential for <analogue work, fixing SMPSUs, etc. But I don't find it _that_ useful on <typical non-repetitive digital signals. Depends, very handy for looking at some timing problems and general bus havoc. <Don't bet on it. I've lost count of the number of misdesigned (often <subtly - like marginal timing or ground bounce problems) DRAM cards that <I've had to sort out. Those cards never worked, as in they often were unreliable or at best a question. S100 cards generally were either solid or sick to my expereince. It may have required running them for a day or two to see that they were not good 24x7 designs. <Also, a logic probe won't detect _some_ chip failures. You've got a 2 <input NAND gate. The logic probe shows nice pulse trains on all 3 <connections. You think it's OK and move on. What it hasn't told you is <that one input does nothing, and the gate is a simple inverter on the <other input. Yes, I've seen exactly that fault. Same here, bad inputs are tough to shoot, though a chip clip (16pins 16 leds) does help here. Allison

26 years, 6 months

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2002

2001

2000

1999

1998

1997

test-drb