test-drb April 2008

test-drb@ccmp.vtda.org

196 participants
307 discussions

by pichotjm＠free.fr

Hi, Pls, have a look at this description of Signetics 25000 series 9046 XN component: http://pichotjm.free.fr/humr/2.html Can you explain me, what is Vff? Is it a good idea to decrease this voltage in order to increase reliability? But what will happen with our 50 Hz european supply? I need help... (please, answer with simple english) JM Pichot

16 years, 8 months

Looking for a M8330 or a couple of SN74194's

by RodSmallwood＠mail.ediconsulting.co.uk

Not only did Cricklewood have them, but they arrived Saturday morning. That effected a partial fix. The timing generator is a string of four bit shift registers clocked with 20Mhz. Various combinations of their outputs are used to set and reset bistables made out of cross coupled 7440's. As the problem I'm fixing is you can't load memory, which is a one shot operation, its slow old work. A spare 8330 would confirm if that's where the problem is and I expect would speed up the repair on the current one. I'll continue with fixing it and keep an eye open for a spare. Getting one from the US would be an option. I also return all systems to working order. Apart from a couple of VT420's with ticking SMPSU's everything I have restored runs. (Three VAX's, Two alphas, a Rainbow 100+, DECMateII, Pro350, Pro380, a DS3100, a VS3100 and assorted LA printers and VT terminals) Rod -----Original Message----- From: cctech-bounces at classiccmp.org [mailto:cctech-bounces at classiccmp.org] On Behalf Of Tony Duell Sent: 28 March 2008 22:52 To: cctalk at classiccmp.org Subject: Re: Looking for a M8330 or a couple of SN74194's > > Hi Tony > I agree that the concept of originality is important in what we do. > The system I have is original in the sense that all the parts are from > the right era. However the current configuration is not that as stated > on the factory label. You could also say that any item with a If this is the machine I think it is, I know not only the chap you got it from, but also the owner before that. IIRC, it originally had a TU56 (single drive versiun, and no I don't mean a TU55) which is currently on my desk, hooked up to my PDP8/e. And the RX8/e is not original. If you look at one of the CPU logic boards, you'll see one of the chips (I forget what) has been replaced. I did that over 10 years ago to cure a problem with the top 4 data lines in some operation or other. The TU56 was 'payment' for that repair... > date of later than the manufacturing date and not the result of a > repair or upgrade is not original. True, and some museums, alas, take it that way, and refuse to instal replacement parts to keep their machines going, even if said parts are contemporarty with the machine. Personally, I like all my classics to run. However, I also like to use as few spares as possible. If your clock generator was missing, or physically cracked in half, or... then I would agree you need an M8330 board. But if you can get your old one to run again, even by using more modern parts (I would have no problems fitting LS chips if they would work electrically, for example), then I'd rather keep the spare board for somebody who really did need it. > > Thanks for the tip re Cricklewood I will contact them. They may only have LS or something like that. As I said, I needed some 7495s, a rather oscure shift register chip that I couldn't find anywhere. They had 74LS95, which worked fine in my HP9820. OK, not original, but at least I can use the machine again. -tony

16 years, 8 months

PDP 11 RL11/01 Address confusion.

by tshoppa＠wmata.com

Johnny writes: > The PDP-11 CPU is a 16-bit machine, so all code will always just deal > with 16-bit values. > > The PDP-11 can have different buses, with different behaviours, but > basically we can divide them into three groups. > 16-bit bus > 18-bit bus > 22-bit bus > > Machines with a simple 16-bit bus is almost nonexistant, but there was > some early Q-bus CPUs with a pure 16-bit address range, I seem to remember. > > 18-bit means all Unibus machines, as well as some Q-bus machines. > > 22-bit means most Q-bus machines. Obviously written from a 11M+ user's perspective. Ignore all those puny Unibus and Q-bus machines without MMU, will you? But they still run RT-11 just fine! Lots of Unibus and Q-bus and not-anything-bus-11's all do quite fine with 16 bit address spaces. While the Unibus electrically has 18 address bits from the get-go, the Unibus 11's without memory management (or without the memory management option) don't use the last two. Even "later" Unibus CPU's like the 11/04 still came without MMU (and it was not an option, either!) Obviously "early" and "later" are taken to be Lasnerian. Tim.

16 years, 8 months

Looking for a M8330 or a couple of SN74194's

by RodSmallwood＠mail.ediconsulting.co.uk

I don't suppose you still have the old M8330 do you? Rod -----Original Message----- From: cctech-bounces at classiccmp.org [mailto:cctech-bounces at classiccmp.org] On Behalf Of Charles H Dickman Sent: 02 April 2008 02:01 To: On-Topic and Off-Topic Posts Subject: Re: Looking for a M8330 or a couple of SN74194's Tony Duell wrote: > DEC scheamtics have the odd error on them (I've heard it claimed said > errors are deliberate, either to stop the machine being copied, or as > copyright traps on the diagrams themselves). They're also somewhat > unconventionally drawn (flip-flops may appear to have 4 outputs!), but > I've got used to them. I must say that if I need to re-draw a > sechematic, I use pen and paper, not a CAD system... > A year and a half ago I was playing with a PDP-8/e and trying to get an EAE working with it. I ended up needing a later version M8330. My original boards were rev 1 and the EAE didn't work until about rev 3. The drawings I found online were WAY different than the boards I had. For the EAE, it looked like there were some serious timing issues, so the later board revisions were quite significant. So, if your boards don't match the drawing rev, don't expect there to be a match. -chuck

16 years, 8 months

Looking for a M8330 or a couple of SN74194's

by RodSmallwood＠mail.ediconsulting.co.uk

Hi Having worked for DEC for a number of years I'm used to the odd logic symbols. They do explain them in the manual. I don't use a CAD system but something much more useful. Visio. Define a DEC logic symbol once, add connection points in the right places, drop as many copies as you need, join connection points and print on A0 paper. Modify drawing as much as you like and print a new copy each time. Iv'e moved the boards back a bit and as soon as I get a few mins I'll see if I can spot why it won't write to memory. Rod -----Original Message----- From: cctech-bounces at classiccmp.org [mailto:cctech-bounces at classiccmp.org] On Behalf Of Tony Duell Sent: 01 April 2008 20:31 To: cctalk at classiccmp.org Subject: Re: Looking for a M8330 or a couple of SN74194's > > Hi > Its not test gear that's the problem its access to the board. My Tek > 465 will trigger on single pulses with no problem. > However whilst it's recommended that the the first CPU board (the > 8330) be in slot 2 (The front panel is in No1) its not mandatory. So I > can move the boards back a bit and get to the front of the 8330. All Omnius slots are the same, and in an 8/e backplane, AFAIK all slots are plain Omnibus. The only time the top connectors are used on the M8330 is if you have the EAE board set installed, I think. If you do, take it out for the moment (you don't need it when trying to sort out a timing generator problem). You can then put the M8330 in whatever slot you want. An extender board is useful, but by no means essential :-). Another trick that's worked for me in the past if I can't re-arrange the boards and don't have an extneder is to solder a hnadful of wires to useful testpoints on the board and put it back in the cardcage. Then probee the free ends of the wires (make sure they don't short to anything!). Normally 2 or 3 iterations of doing that will get me to the faulty chip. > > Manual I have, (very good) Schematics also (Awful) so bad I may even > redraw at least the 8330. I have an A0 HP plotter so its easy to do > drawings. DEC scheamtics have the odd error on them (I've heard it claimed said errors are deliberate, either to stop the machine being copied, or as copyright traps on the diagrams themselves). They're also somewhat unconventionally drawn (flip-flops may appear to have 4 outputs!), but I've got used to them. I must say that if I need to re-draw a sechematic, I use pen and paper, not a CAD system... -tony

16 years, 8 months

What is a FINO? Need about Vff.

by pcoghlan+cctech＠vms.eurokom.ie

pichotjm <pichotjm at free.fr> wrote: > >Pls, have a look at this description of Signetics 25000 series 9046 XN >component: http://pichotjm.free.fr/humr/2.html It is not always necessary to go to the expense of buying a 25000 series chip. I found some WOM in my Dec Alphaserver 1000A recently. I'm not interested in this bleeding-edge stuff (besides its too new to be on-topic here) so I have now replaced it with some ordinary memory. I wonder if I could get a good price for the WOM on ebay? >Can you explain me, what is Vff? Is it a good idea to decrease this voltage >in order to increase reliability? 6.3Vac is a common voltage for valve (tube) filaments. Given that the 25000 series is implemented in VLSI (Vacuum large scale integration), I suspect Vff is the supply to the filaments for the integrated valves on the WOM chip. Decreasing Vff should reduce power dissipation and improve the lifetime of the chip. However, it may also result in poorer noise immunity. Either that or Vff is the reference voltage used by the flip-flops and decreasing it will unbalance the chip by creating an excess of flops over flips. >But what will happen with our 50 Hz european supply? Typically, these things are designed for the American market with no thought given to widely used standards in other parts of the world. I suspect we will have to use motor-generator sets to power this type of circuit. Solid state frequency converters will not be suitable for the critical power requirements here. >I need help... > >(please, answer with simple english) > >JM Pichot > Regards, Peter.

16 years, 8 months

Adding a 3rd floppy to an old PC SCSI controller

by cclist＠sydex.com

Dwight asked: > Pardon me for asking but are you sure the chip can provide > enough drive? Most floppies expect to terminal with about > 150 Ohms. That is more than an unbuffered output of most > chips are designed for. > Just asking? Good point--but the datasheet states right in the opening remarks that it can be connected directly to the disk drive with its own internal 48 ma buffered output and schmitt inputs. The datahseet's easy to find on the web--several places have it. Here, for example: http://www.tranzistoare.ro/datasheets2/36/366021_1.pdf I like the DP8473--unlike the Intel 82077AA and later chips, it still knows how to do FM correctly--and will even write 128 byte sectored MFM, which is something that Intel was ever able to do. Don Maslin and I worked through a pile of FDC chips before we found this one. I think there was a Future Domain card (1680?) that brought all 4 floppy drives out to 2 headers--and I certainly could have added one to do that myself for 4 drives, but 3 on one cable was the easiest. Cheers, Chuck

16 years, 8 months

PDP 11 RL11/01 Address confusion.

by doug＠stillhq.com

Hi Everybody I was reading some doco last night (specifically the DEC RL11/01 Disk Subsystem Training Handout), and I am confused. (That is nothing new...) In the "Subsystem commands section", the addresses specified for DAR and CSR are 774404, and 774400 respectively, but in the back of the document, under the 'toggle in programs' section, the DAR and CSR are shown as being at 174404 and 174400 respectively. Hmmm. I see three possibilities: 1. I have (re) discovered a documentation error - I wonder if DEC, no, HP, no Compaq, would be happy for me to submit an amendment :-) 2. The hardware throws away the upper bits so both references are correct. Hmmm Possibly not :-) 3. There is some other stuff happening that I missed... If anybody could shed some light on this I would appreciate it. The background to the problem is that I can not convince my shiny, wonderful, (and noisy) DL01 to perform the seek test - Me thinks there is a problem.... Doug

16 years, 8 months

Looking for a M8330 or a couple of SN74194's

by RodSmallwood＠mail.ediconsulting.co.uk

Oh I forgot.. The 420's .. I have not done anything because a) It only happened last week b) I cant find any drawings. Rod -----Original Message----- From: cctech-bounces at classiccmp.org [mailto:cctech-bounces at classiccmp.org] On Behalf Of Tony Duell Sent: 31 March 2008 22:52 To: cctalk at classiccmp.org Subject: Re: Looking for a M8330 or a couple of SN74194's > > > Not only did Cricklewood have them, but they arrived Saturday morning. I'm even luckier in that I live near enough to Cricklewood Electronics that I can pop over there and pick the chips up the same day ;-) > That effected a partial fix. > The timing generator is a string of four bit shift registers clocked > with 20Mhz. OK. > Various combinations of their outputs are used to set and reset > bistables made out of cross coupled 7440's. > As the problem I'm fixing is you can't load memory, which is a one > shot operation, its slow old work. I don;t know what test gear you have, but I find a simple logic probe to be more use than a 'scope for this sort of problem. The former can easily detect narrow pulses that are difficult, if not impossible, to see on a non-storage 'scope. Of course an 'Advanded Logic Probe' as HP called the LogicDart is even nicer, but... Do you have the maintenance manual? Not the printset (schematics), but the book which is a low-level circuit description? It's well worth reading!. I would have thought it wouldn't be too hard to keep on hitting the DEP key and seeing what, if any Omnius signals are generated. And then totrace back the missing one(s). [...] > I also return all systems to working order. Apart from a couple of > VT420's with ticking SMPSU's everything I have restored runs. (Three Any reason you';ve not fixed those? Ticking SMPSUs are often quite simple to fix, maybe just dried-up capacitors. -tony

16 years, 8 months

Adding a 3rd floppy to an old PC SCSI controller

by cclist＠sydex.com

> Date: Tue, 1 Apr 2008 10:47:25 +0200 (CEST) > From: Christian Corti > The 8473 directly supports four drives, so you can do the "trick" a second > time for a fourth drive. And even some motherboard Super I/O chips have > support for four drives, the outputs are simply not used. My needs and the number of spare conductors on the cable simultaneously gave out with 3 drives. Somewhere in my collection I've got a controller (may not even be SCSI; could be ESDI or MFM/RLL) that had a jumperable option to drive 4 floppies from a single cable by using the drive select jumpers and a common motor control line. The two downside issues are that your drives have to have 4 drive selects (or you had to be clever with your cable twists) and when one motor comes on, they all do. Better to use two headers and two cables, IMOHO. Cheers, Chuck

16 years, 8 months

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test-drb April 2008