RE: ZX Spectrum Z80 Keeps Resetting
> As I recall with the ZX Spectrum there wasn't any "snow" on TV with a > subsequent reset (as when pressing the reset button on the Plus variation). > > Moreover DRAM refresh continued to work (presumably being driven by the R > register of the Z80 CPU according to its machine cycles, although at this point > I'd have to double check the details as my brain actually seems to be missing > the R register altogether), so unlike with a power-up reset, where you'd initially > get random rubbish on the screen, with a subsequent reset you'd see a black > rectangle (with thin vertical stripes IIRC, meaning a pattern with a single bit > set) instead as the part of memory used for video data gets cleared in the > DRAM initialisation process, followed by the copyright notice you mention. > > That you see "snow" instead is I believe indeed a strong indication that > something else goes wrong beyond (or instead of) just an intermittent reset. > And given that the ULA produces video output right away after power-up with > no need to program any device registers is I think an indication that either the > chip is broken or something else causes it to malfunction, just as you have > concluded. > Thanks Maciej. Since I never had Spectrum when they were new, I didn't know that this was how it behaved on a reset. I am glad that my analysis seems to be on the right track (given what I know at the moment). I am going to concentrate on the ULA and the video output, but given that the keyboard also doesn't seem to work the ULA has to be the prime suspect at the moment. I am still hoping someone will know if I can try swapping the ULA with a newer one from a later model I have. I may also look at getting a NebULA as they are not expensive. Regards Rob
Re: 40 pin Berg cable connector recommendations for PDP-11 projects?
good timing to ask. i ordered a similar connector that should do the job off digikey. i am still waiting for it to get here in the mail. It was $20 or so after ordering the pins and the shipping. the particular connector i ordered has a key on it that will need to be filed off to fit. once it gets here and i am certain it will fit properly i can get you the part #. should be a day or two more before it gets here. On Jan 3, 2018 5:55 PM, "Fritz Mueller via cctalk" wrote: > Hello PDP-11 crowd: > > I’m thinking of starting a project that will interface to a DR11-C, which > has the usual 40-pin Berg ribbon cable connectors. I thought I’d ping the > collected wisdom here to see if other folks had already sourced an > available modern cable connector for this that they particularly like? > > cheers, > —FritzM. > > > >
Re: DEC H960 stabiliser feet. Have some questions.
From: Steve Malikoff via cctalk: Wednesday, January 03, 2018 3:26 PM Vince - thanks for the measurements, I will redraw a better 3-view using those. Not sure about how the extra bolt goes though. You're welcome, and thanks for your work on the drawing. One thing I forgot to mention -- on mine, the path from edge "D" to edge "G" is a diagonal, not a right angle. That is, "K" starts at zero, and grows to 1.0 inches at the tip where "G" is measured. The thickness there looks similar to the thickness at "G". (The metal stiffens the flanges in both directions, preventing bending or breakage.) The extra bolt has a slotted flat screw head with a maximum diameter of about 0.6" at the top edge, centered in the "D" direction, and about 0.6" forward in the "K" direction. I'd have to get out some tools and take one apart to measure it's length and thread, but it looks like a standard DECish thread to my eye (#10-something?), and protrudes just a few threads past the nut on the bottom. Vince
Re: 40 pin Berg cable connector recommendations for PDP-11 projects?
Chuck is right on about having the right tools. I use a Paladin (now Greenlee) PA1645 for most of my wire housing crimp terminal needs. I've got an older Weidmuller Mini Stripax wire stripper that works excellent, bought it after having used one in a job in college. I don't use the "official" tool for IDC connector crimping, though -- I use a small arbor press. Picked it up at the MIT Flea for under $20. Thanks, Jonathan On Wed, Jan 3, 2018 at 7:11 PM, Chuck Guzis via cctalk < cctalk@classiccmp.org> wrote: > On 01/03/2018 03:03 PM, systems_glitch via cctalk wrote: > > Most IDC connectors will fit just fine. I've use old 40-pin IDE cables > > before. Beware that the keying boss may be too short for the old blue > Berg > > housings, allowing the cable to be inserted upside-down (don't depend on > > the keying boss!). > > > > There are wire housing type connectors you can get, as well, which allow > > individual pins to be crimped to wires and then inserted into the > housing. > > Mouser's parametric search will yield many options. > > Also, be aware that twisted-pair ribbon cable may be specified on some > of this older stuff. Depending on the length of the run, "straight" > ribbon cable may work, but it's something to pay attention to if you're > in the 10-20 m lengths. > > I use the crimp pins and housings all the time. Recently, I had a > dual-row 8 pin module to plug into another board. I used the female > Berg housing and pins crimped onto lengths of AWG 18 solid wire, which > in turn was soldered to the PCB. It saved me from having to order a > special female header. > > If you do go the crimp-pin route, get yourself a good crimper made for > the job.--I use one made by/for Molex--it's a spring-loaded ratchet > affair that repeatedly crimps the pins very neatly. > > The other thing is to get a good wire stripper that won't nick the > conductors. I use the "Micro Strip" tool that's often used for > stripping fiber jackets--I originally got mine for stripping wire-wrap > wire. > > You can sometimes find these tools on the used market. New, they can be > quite dear. > > --Chuck > >
RE: ZX Spectrum Z80 Keeps Resetting
On Wed, 3 Jan 2018, Rob Jarratt via cctalk wrote: > The reason I say this is that when I set up the logic analyser to *stop* > on a zero ROM address, it didn't. Which means it isn't resetting in the > way I thought it was. When I traced the instruction addresses during > boot up I could see lots of resets back to address zero, and assumed > that somehow it was getting further into the sequence to show the > copyright screen, but then resetting again, because the screen would > display the "snow" after showing the copyright screen. As I recall with the ZX Spectrum there wasn't any "snow" on TV with a subsequent reset (as when pressing the reset button on the Plus variation). Moreover DRAM refresh continued to work (presumably being driven by the R register of the Z80 CPU according to its machine cycles, although at this point I'd have to double check the details as my brain actually seems to be missing the R register altogether), so unlike with a power-up reset, where you'd initially get random rubbish on the screen, with a subsequent reset you'd see a black rectangle (with thin vertical stripes IIRC, meaning a pattern with a single bit set) instead as the part of memory used for video data gets cleared in the DRAM initialisation process, followed by the copyright notice you mention. That you see "snow" instead is I believe indeed a strong indication that something else goes wrong beyond (or instead of) just an intermittent reset. And given that the ULA produces video output right away after power-up with no need to program any device registers is I think an indication that either the chip is broken or something else causes it to malfunction, just as you have concluded. FWIW, Maciej
Re: 40 pin Berg cable connector recommendations for PDP-11 projects?
On 01/03/2018 03:03 PM, systems_glitch via cctalk wrote: > Most IDC connectors will fit just fine. I've use old 40-pin IDE cables > before. Beware that the keying boss may be too short for the old blue Berg > housings, allowing the cable to be inserted upside-down (don't depend on > the keying boss!). > > There are wire housing type connectors you can get, as well, which allow > individual pins to be crimped to wires and then inserted into the housing. > Mouser's parametric search will yield many options. Also, be aware that twisted-pair ribbon cable may be specified on some of this older stuff. Depending on the length of the run, "straight" ribbon cable may work, but it's something to pay attention to if you're in the 10-20 m lengths. I use the crimp pins and housings all the time. Recently, I had a dual-row 8 pin module to plug into another board. I used the female Berg housing and pins crimped onto lengths of AWG 18 solid wire, which in turn was soldered to the PCB. It saved me from having to order a special female header. If you do go the crimp-pin route, get yourself a good crimper made for the job.--I use one made by/for Molex--it's a spring-loaded ratchet affair that repeatedly crimps the pins very neatly. The other thing is to get a good wire stripper that won't nick the conductors. I use the "Micro Strip" tool that's often used for stripping fiber jackets--I originally got mine for stripping wire-wrap wire. You can sometimes find these tools on the used market. New, they can be quite dear. --Chuck
Re: QSIC update and request, 11/04 microcode
On 2018-01-01 13:42, David Bridgham via cctalk wrote: I'd rather not get diverted by yet another substantial development project so I'm looking for a decent little FPGA implementation of a PDP-11 that I could just pick up use for this purpose. Something that's already debugged. I'm thinking closer to an 11/04 than an 11/70 and likely just running out of block RAM on the FPGA. is the 11/04 microcode somewhere as a binary? So far I found only the print in the MPS ...
Re: DEC H960 stabiliser feet. Have some questions.
Excellent, that's a great start. Vince - thanks for the measurements, I will redraw a better 3-view using those. Not sure about how the extra bolt goes though. Ethan - thanks for confirming the different leg pad to frame pad. Noel - that is extremely useful info on the pads, I've now found them at http://www.vlier.com/product_index/leveling/sel_05_lstar.html# Paul - yes I noticed some systems had different legs, for instance this one https://c1.staticflickr.com/3/2435/3878202215_372c46fccb_b.jpg and any p/n info you have from better sources would be welcome. The part number I found for the legs (H-952-BA) came from the Fall 1978 Digital Sales Catalog, page 129 which has the same p/n for both Standard and Short cabinets. I'll cogitate over a revised drawing and get back to the list. Thanks again, Steve.
Re: 40 pin Berg cable connector recommendations for PDP-11 projects?
Most IDC connectors will fit just fine. I've use old 40-pin IDE cables before. Beware that the keying boss may be too short for the old blue Berg housings, allowing the cable to be inserted upside-down (don't depend on the keying boss!). There are wire housing type connectors you can get, as well, which allow individual pins to be crimped to wires and then inserted into the housing. Mouser's parametric search will yield many options. Thanks, Jonathan On Wed, Jan 3, 2018 at 5:55 PM, Fritz Mueller via cctalk < cctalk@classiccmp.org> wrote: > Hello PDP-11 crowd: > > I’m thinking of starting a project that will interface to a DR11-C, which > has the usual 40-pin Berg ribbon cable connectors. I thought I’d ping the > collected wisdom here to see if other folks had already sourced an > available modern cable connector for this that they particularly like? > > cheers, > —FritzM. > > > >
Sellam's Manual, Book, Magazine and General Documentation Sales Thread
Greetings from the piles! I've created a new thread on the VCFed forums for listing manuals, books, magazines and general computer related documentation. The thread is here: http://www.vcfed.org/forum/showthread.php?61380-Sellam-s-Manual-Book-Magazine-and-General-Documentation-Sales-Thread Thanks! Sellam
40 pin Berg cable connector recommendations for PDP-11 projects?
Hello PDP-11 crowd: I’m thinking of starting a project that will interface to a DR11-C, which has the usual 40-pin Berg ribbon cable connectors. I thought I’d ping the collected wisdom here to see if other folks had already sourced an available modern cable connector for this that they particularly like? cheers, —FritzM.
Re: DEC H960 stabiliser feet. Have some questions.
I would be interested in a few dozen of the cabinet feet and maybe 18 for the stabilizer feet. I seem to recall looking at a few of the stabilizer feet a few months ago and noticing there were a few different versions. I will try to find my cabinet handbook and see what it says, and supply DEC part numbers if anyone is interested. Paul On Wed, Jan 3, 2018 at 11:11 AM, Noel Chiappa via cctalk < cctalk@classiccmp.org> wrote: > > From: Ethan Dicks > > > The rod is also smaller by quite a bit, but I don't have one in front > > of me to measure. > > The two feet are quite different. The smaller one on the extender is > 5/16"-18 > (i.e. UNC Coarse thread); the larger one under the cabinet is 1/2"-13. > > Replacements can easily be had from Vlier: Vlier part numbers are FSE302S > (for the extender feet), and FSE306S (for the main feet). > > > We really ought to do a group bulk build of the extension castings; if we > get > a reasonable size order together, they shouldn't be that expensive. Ditto > for the special bolt needed to hold them to the H960. > > Noel >
RE: ZX Spectrum Z80 Keeps Resetting
I am beginning to wonder if the problem might be the ULA. The reason I say this is that when I set up the logic analyser to *stop* on a zero ROM address, it didn't. Which means it isn't resetting in the way I thought it was. When I traced the instruction addresses during boot up I could see lots of resets back to address zero, and assumed that somehow it was getting further into the sequence to show the copyright screen, but then resetting again, because the screen would display the "snow" after showing the copyright screen. So if it isn't resetting then something may be just interrupting the video display, and the machine just thinks it is showing the copyright screen and waiting for input. This is further evidenced by the fact that the ROM addresses when it is in this cycle all seem to be in the keyboard input area, based on a PDF that documents a disassembly of the ROM that I found on the web. If that was the case I thought it might respond to keypresses, but I checked and it doesn't, and the same happens with a second keyboard from another machine. However, the ULA is responsible for the video signal and for the keyboard input, so it suggests the ULA, or something around it, could be the problem. I have a second Spectrum (with a different fault that I think is the memory) that is a later design. It has the 6C001E-6 ULA, the older machine (which appears to reset) has a 5C112E ULA. Looking at this page http://www.bytedelight.com/?p=41 the 6C001E-7 (not -6) ULA can be used on older machines. Does anyone know if, just as a test, it would be safe to put the newer 6C001E-6 ULA in the older machine? Fortunately both ULAs are socketed, so this would be an easy test. Thanks Rob
Re: DEC H960 stabiliser feet. Have some questions.
> From: Ethan Dicks > The rod is also smaller by quite a bit, but I don't have one in front > of me to measure. The two feet are quite different. The smaller one on the extender is 5/16"-18 (i.e. UNC Coarse thread); the larger one under the cabinet is 1/2"-13. Replacements can easily be had from Vlier: Vlier part numbers are FSE302S (for the extender feet), and FSE306S (for the main feet). We really ought to do a group bulk build of the extension castings; if we get a reasonable size order together, they shouldn't be that expensive. Ditto for the special bolt needed to hold them to the H960. Noel
Re: DEC H960 stabiliser feet. Have some questions.
On Wed, Jan 3, 2018 at 10:28 AM, Vincent Slyngstad via cctalk wrote: > From: Steve Malikoff via cctalk: Tuesday, January 02, 2018 6:24 PM >> >> I'm in need of some feet for my H960s and am intending to make a few >> pairs, so I thought I might as well try and make them look close to the >> originals. > >> Is the foot pad thread in the centre of the front of the leg, and is it >> the same thread and pad as the H960? > > Yes. The foot pad is smaller, but without removing the one on the > rack it is hard to compare the threaded rods. The rod is also smaller by quite a bit, but I don't have one in front of me to measure. -ethan
Re: DEC H960 stabiliser feet. Have some questions.
From: Steve Malikoff via cctalk: Tuesday, January 02, 2018 6:24 PM I'm in need of some feet for my H960s and am intending to make a few pairs, so I thought I might as well try and make them look close to the originals. I have some questions- Does the (optional?) sheetmetal kickplate play any role in securing these legs to the frame? I assume by kickplate you mean that piece of square channel that is bolted to the bottom front of the rack. My feet seem to be bolted to it and through it. Are the two front screws are only there to hold them on and there is some internal box section that goes into the front of the channel on the rack to take the weight? There's a large fastener (machine screw with a large flat head) running through the channel with a nut at the bottom, as well as two screws to keep it from pivoting to the side. Some of my kickplates have both front screws and holes, and some only the upper hole. Is the outer side tapered? It looks straight. Straight. If the foot a one piece casting (presumably) or fabricated in some way? It looks like a one piece casting. Is the foot pad thread in the centre of the front of the leg, and is it the same thread and pad as the H960? Yes. The foot pad is smaller, but without removing the one on the rack it is hard to compare the threaded rods. Finally I would really appreciate if someone could run a digital caliper over one, and fill in my required measurements A through Q in the above drawing. And if you have a radius guage that would really be great. A is about 9 1/8 inches. B is 2 3/8 inches. C is about 2.1 inches. D is 1.45 inches. E is 1.3 inches. F is 1.25 inches. G is approximately 0.2 inches. H is 0.9 inches. The threaded rod for I has a diameter of 0.305 inches. If J is meant to be the foot pad, the radius is 0.6 inches. K is 1.0 inches. Radius L is approximately 1/4 inch. If M is meant to be the corner bevel, those are a tight corner that I can't measure accurately. N is likewise a tight corner that I don't have a tool to measure. I didn't find an "O". P is also too tightly rounded for me to measure. Q has a 1/8 inch radius. Hope that helps! Vince
