test-drb

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101090 discussions

by allisonp＠world.std.com

< > terminator. Do all S-100 buses require external termination, or did m < Only the motherboards that didn't have active termination require a < terminator. In my experience, that's a fair number of mobo's out there My experience with 4 or 5 crates I have and many I've built up. If it runs well or the bus looks clean to the O'scope skip it. Some busses it's helps but still look terrible (altair with the original backplanes). My Northstar Horizon never needed one and it's currently running at 8mhz. The VectorMX box I have with Compupro backplane needed the terminators installed for 10mhz. The CCS I'm using with discus hard disk and 8" floppy doesn't require it at 4mhz or 6mhz. One thing that seems to be true, the longer the backplane the more likely it will ring and need termination. All Altairs seem to and IMSAIs seem to benefit if the cpu is z80 4mhz. The quietest unterminated or terminated backplane I own is an oddball 6 slot I have that is 4 layer technology with ground and power are on the middle two layers. I've found a few badly designed cpu cards and memory cards that were terrible in that they would introduce noise onto an otherwise quiet bus! Allison

28 years, 1 month

FW: Writer wants to quote users

by allisonp＠world.std.com

< So, can a standard XT controller be used for 8" drives? No/yes but, it is one that is documented and modifyable. So happens I was with NEC Microelectrnics when they introduced the 765 chip so I sorta have an advantage when it come to floppy interfacing. < For once, I used the correct terminology :) Compared to SCSI, all < IDE controllers and most non-IDE/SCSI MFM drives require very little < configuration. That's what I meant. False truism. They are about the same just differnt. IDE with the limitation of two drives really does limit the variable parameters. MFM with up to 4 drives and two schemes for addressing have to have more. SCSI you have a device address, powerup mode and a few others like termination to select from. < So does this mean 1.2MB floppies use a lower bps than 360K disks? < Which controllers were these? I ought to watch out. no. All of them. Allison

28 years, 1 month

IBM Power supplies FS (5140?)

by cgregory＠lrbcg.com

I can confirm that is indeed the part number for a 5140 power supply. If you look on the back of the power supply itself you will see IBM's declaration that it should be only used with model 5140 (in several languages!). I wouldn't mind having a spare myself. I'll contact you directly. Cliff Gregory cgregory(a)lrbcg.com -----Original Message----- From: classiccmp(a)u.washington.edu <classiccmp(a)u.washington.edu> To: Cgregory <Cgregory> Date: Friday, July 24, 1998 10:41 PM Subject: IBM Power supplies FS (5140?) > >Hi guys, > I just picked up a bunch of IBM power supplies at auction. The >auctioneer says they're for the 5140, but I don't know how you could tell. > > They're all appear to be brand new and are in the original boxes. The >box is labeled "P/N 2684220", the Power supply "P/N 2684292". Output is >15v, 2.7A. > >Anybody know what they're for? And if anybody wants one, the price is $5 >shipped, each. > >Tom Owad > >-- >Sysop of Caesarville Online >Client software at: <http://home.earthlink.net/~tomowad/> > >

28 years, 1 month

IBM Power supplies FS (5140?)

by mbg＠world.std.com

> I just picked up a bunch of IBM power supplies at auction. The >auctioneer says they're for the 5140, but I don't know how you could >tell. The 5140 is the IBM PC Convertible 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 | +--------------------------------+-------------------------------------+

28 years, 1 month

FW: Writer wants to quote users

by pete＠dunnington.u-net.com

On Jul 25, 8:08, Pete Turnbull wrote: > Some of those HD drives can be switched between 300/360 > rpm by the signal on pin 1 of the interface, .... ...but he meant pin 2 :-) -- Pete Peter Turnbull Dept. of Computer Science University of York

28 years, 1 month

semi-off topic: how to put a 5-1/4" or 8" in those newfangled PII easy-bake oven boxes

by chris＠microgear.net

> < That's an immense exaggeration. P-II boxes a) Have no jumpers, as a > < rule b) can support a 5.25" fdd if you can plug one in. > > Why the "if you can plug one in"? Will plug and puke really work? What > do you do if it doesn't? What slot does the 8" controller from the XT > plug into on the PCI only board? > not to butt in here, but this is what i do for a "real job" so here goes... if the cable has the card-edge plug on it (or you have an adapter) the pII bioses still support 5.25" floppy, it's not plug & play, you have to tell the bios it has it AFAIK. Most drive cables still have the card-edge connector on the slot for the B: drive, too. And I have only seen one all-PCI board, most retain at least 3 isa slots because of modems and the like, so the 8" controller, if need be, would go there (I presume, never dealt with one on a PC) It's just that nothing of consequence to your average pentium II user is on anything with less capacity than a CD (with the advent of Windows 98, even the boot floppy for the first system install has become obsolete, and we can all thank Bill Gates and his fat programs for that) anymore, so you rarely see the old 5 1/4"s in those systems. But it *could* be done, and without much difficulty. Chris

28 years, 1 month

FW: Writer wants to quote users

by pete＠dunnington.u-net.com

On Jul 24, 18:02, Max Eskin wrote: > So, can a standard XT controller be used for 8" drives? You need a little adapter to shuffle the signals from the 34-pin connector to a 50-pin connector, but usually that's all. The data rate for an 8" DD (MFM) disk is the same as for a 3.5" HD (also MFM) disk. If you want to use 8" SD (FM) disks, you may need to add a jumper to the controller, as not all XT controllers can handle single-density. > So does this mean 1.2MB floppies use a lower bps than 360K disks? > Which controllers were these? I ought to watch out. Other way round. The 360K disks (better called 40-track double-sided) normally run at 300 rpm and (for MFM/double density) use a data rate of 250 bps. Before HD disks, 80-track disks were made the same way. Most HD drives, though, switch to 360 rpm and use a data rate of 300 bps (or 600 bps in HD mode). Some of those HD drives can be switched between 300/360 rpm by the signal on pin 1 of the interface, which is used for DD/HD selection. -- Pete Peter Turnbull Dept. of Computer Science University of York

28 years, 1 month

S-100 bus termination

by rigdonj＠intellistar.net

Doug, Since I got my Altair, I've been boning up on the s-100 stuff. I got an active terminator board with my Altair so that's one thing that I paid particular attention too. Here's what I found out. The first S-100 computers did not come with any termination but they soon found that the long bus lines were causing ringing and false triggering in the circuits. Ringing is caused when a signal reaches the end of an unterminated (open) line such as a data buss.* The signal reverses polarity and travels back in the direction that it came from just like an echo. When it reaches another end, it changes polarity and direction again. Now you have two positive pulses and one negative pulse where there is only supposed to be one pulse! Consider the number of times that each line branched off to a card socket and you can understand that now there where a dozen or more echos on every line and they were all at different times. It's no wonder that the systems where so difficult to make work with all the noise on the buss. The first solution was to use passive termination to try and eliminate the noise but it had limited success. This method used resistor divider networks that connected to the 0 and 5 volt power with the junctions connected to the signal lines. They had to keep the resistances high to minimize power supply loading and to prevent clamping the line so well that no signal could get through. This method wasn't entirely effective due to the combination of high clamping impedence (resistance) and unterminated branchs (sockets). The next solution was to use active termination. This method uses what amounts to small individual power supplies on each line to hold the line voltage at a level between 0 and the maximum siganl level (5 volts). This method offered a lower clamping impedence AND less power supply loading and was better able to prevent the ringing. The active terminator baords were a very popular accessory and a lot of people where making and selling them. In fact, I have an article from one of the first Byte magazines about how to make your own active terminator board. I believe that the later S-100 systems like the N* Horizon came with termination built into the MB. The ringing problem in the early Altairs was made worse by use of the long wires that ran from the MB to the front panel. Better designs eliminated a lot the sources of the ringing. FWIW this is EXACTLY the reason that you still have to terminate SCSI busses and disk drive cabling. There is still an ongoing debate in the SCSI community about the nessecity/benefits of active vs passive termination. * OK OK! Just for you purists, ringing is caused ANYTIME a signal makes a transistion from one impedence to another. The bigger the change, the bigger the reflected signal. That's why when ****power**** or signal distortion counts, you have to try and match all the impedences in the signal path. That means that your signal source such as an antenna, the signal destination such as your TV set and the interconnecting cableing all have to have the same impedence or you have to use a matching transformer to match the impedences. Go look at the back of your televison, you'll usually see a matching transformer and 300 Ohm and 75 Ohm inputs. The two inputs are there so that you can use the one that matches the impedence of the lead that brings the signal into your home. Most TV antennas have a 300 Ohm Impedence. The round coaxial cable has an impedence of 75 Ohms. If you are using it then there should also be a small matching transformer on your antenna. Joe At 07:26 PM 7/24/98 -0500, you wrote: >I was digging through some S-100 cards and came upon a Godbout active >terminator. Do all S-100 buses require external termination, or did more >have it built into the mobo? Specifically, do I need to stick this card >into my IMSAI? > >-- Doug > >

28 years, 1 month

FW: Getting rid of 11/84

by kyrrin＠jps.net

Heads up in Midland, Michigan! (or vicinity). This fellow is looking for a "recycler" to get rid of an 11/84. This sounds to me like (1), a prime opportunity for any of our rescue folk in the midwest, and (2), a prime opportunity to educate the fellow getting rid of it that a recycler is not the only answer. Please contact him directly if you can help. Thanks! Attachment follows. -=-=- <snip> -=-=- On Fri, 24 Jul 1998 20:04:52 GMT, in alt.sys.pdp11 you wrote: >>From: yellow_fiero(a)my-dejanews.com >>Newsgroups: alt.sys.pdp11 >>Subject: Getting rid of a PDP-11 follow-up >>Date: Fri, 24 Jul 1998 20:04:52 GMT >>Organization: Deja News - The Leader in Internet Discussion >>Lines: 26 >>Message-ID: <6papd5$kfh$1(a)nnrp1.dejanews.com> >>NNTP-Posting-Host: 208.154.221.12 >>X-Article-Creation-Date: Fri Jul 24 20:04:52 1998 GMT >>X-Http-User-Agent: Mozilla/4.0 (compatible; MSIE 4.01; Windows 95) >>X-Http-Proxy: 1.0 CORPNT45 >>Path: blushng.jps.net!news.eli.net!news-out.internetmci.com!newsfeed.internetmci.com!204.238.120.130!news-feeds.jump.net!nntp2.dejanews.com!nnrp1.dejanews.com!not-for-mail >> >>Sorry about the confusion, the PDP-11/84 is located in Midland, MI USA. We >>have the CPU, two RL02 disk drives, a TK50R tape, and RA81, and roughly 72 of >>each kind of process interface I/O points (analog input, analog output, >>digital input, digital output) with boards made by a company called Computec >>(later called Interautomation - located in Canada). Our DEC runs seven 500 >>gallon mixers, and has done so since the 70s. >> >>I have also found a very old PDP-11 that runs our rs-232 interface. I don't >>have a model number on it, but interestingly enough, I took the top cover off >>and it has wire-wrapped boards!!! I was surprised that it was still running >>our process, but it is! The only stampings on it are the following: >> >>M11 >>BA11E >>S-1285 >> >>located on the back panel. What could this be? >> >>Anyway, I'm still looking for a recycler. I have a complete list of all >>components and model numbers if anyone finds it necessary. Thanks for your >>responses, and I will post this note also. >> >>Robert Most. >> >>-----== Posted via Deja News, The Leader in Internet Discussion ==----- >>http://www.dejanews.com/rg_mkgrp.xp Create Your Own Free Member Forum -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- Bruce Lane, Sysop, The Dragon's Cave (Fido 1:343/272) http://table.jps.net/~kyrrin -- also kyrrin [A-t] Jps {D=o=t} Net Spam is bad. Spam is theft of service. Spam wastes resources. Don't spam, period. I am a WASHINGTON STATE resident. Spam charged $500.00 per incident per Chapter 19 RCW.

28 years, 1 month

FW: WANTED: PDP-11 or PDP-8

by mbg＠world.std.com

>> Can anyone give Seth a good push in the right direction? If so, >> give him a buzz. >I posted this on Usenet specifically so everyone here on 'classiccmp' >could stop being sick of my "I want a PDP!" whining ;) > >Oh well, I'll take what publicity I can get, eh? Heck, you're not the only one who wants an -8... 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 | +--------------------------------+-------------------------------------+

28 years, 1 month

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test-drb