Ethan wrote... Cool! All I need to know now is what size tygon tube to buy :)

Yes, the PDP-11/44 manuals. There aren't "TONS" of those.

Jay West wrote: I believe that the backplane has the grant jumpered, and you have to remove this wire if you want to put a card that uses that signal. That means you don't have to fill your backplane with grant cards if you have the jumpers still on.

--- "Jeffrey S. Worley" <Technoid(a)30below.com> wrote: I think you need to go back in time a bit and consider the original Unibus processors, like the 11/20. It doesn't have single-card periperals, it has peripherals with their own custom-wired backplanes. The Unibus-in and Unibus-out slots were standardized, but in between, it was up to the designer. There's lots of consistency in DEC peripherals - they tended to use M105s and other "standard" Unibus modules, but that wasn't an absolute requirement. In those days, to initiate an NPR cycle (i.e., start a DMA operation), the peripheral broke the connection of the NPR signal between the Unibus-in and Unibus-out slots. When boards began to get more dense and it was finally possible to put an entire peripheral on a single card, these peripherals couldn't operate the same way. The new method was to break the signal between a pair of pins on the same slot. It wasn't possible to ship all new backplanes (like the DD11DK) without the NPR jumper removed because there were some early non-DMA periperals (like the line-printer interface) that may or may not jumper that signal on their own. So... going back at least as far as 1981 (the earliest Unibus COMBOARDs), makers of NPR devices had to provide instructions for the customer on how to locate, remove and replace the NPR jumper wire. We also shipped a wider grant card (the "Grantasaurus Rex" - GC747) so that our customers didn't have to rewire the backplane when our board was not installed. I was told that the original scheme existed because nobody planned for a DMA peripheral that occupied only a single slot - too much hardware to fit in such a small space. It did take a number of years, so the expectation wasn't that unreasonable. -ethan

The Unibus got one thing very right. It allowed multiple devices to share BR (interrupt) and the NPR (DMA) lines. Anyone who's battled with the ISA bus will certainly appreciate this. The various devices on each line are assigned priorities by how 'far' they are from the CPU. The device nearest to the CPU (strictly the arbiter) is the highest, etc. The way this works is very simple. A device asserts the appropriate request line (this line is bussed to all devices). The arbiter asserts the appropriate grant line, which is not bussed. Instead it's connected to the first device. The first device then passes the grant on to the second, and so on. Devices actually asserting the request line (there could be more than one) don't pass on the grant, so that devices further away from the CPU than the first device trying to cause an interrupt never see the grant. This works very well, but it has one problem. You can't have empty slots in the backplane. Instead you have to insert grant continuity cards to link the grant-in to grant-out lines on unused slots, so as to pass on the grant. There are 5 grants on the Unibus, 4 for interrupts (BG) and one for DMA (NPG). Originally, there were no single-card DMA devices -- DMA devices were complete backplanes that you connected into the unibus chain. Therefore the original grant cards only handled the BG lines. Later on, single-card DMA devices became possible, and the NPG line was connected to pins CA1 and CB1 on the normal SPC (Small Peripheral Controller) slot. Hwever, there's a problem in that the older grant cards didn't connect these 2 pins together. Worse than that, nor did any of the older SPC I/O cards. So there had to be another way of linking them together on an empty slot. And that's the wire-wrap jumper I mentioned.There is a later dual-height grant continuity card that does connect the NPG lines as well, but you still have to know how to do the wire-wrap version since any older non-DMA cards (DL11, PC11, etc) require it. Physically the last (leftmost) slot. The other slots may well be wired slightly differently)!. [OK, I know there are exceptions to this, the VT11 being the obvious one, where the terminator goes somewhere totally different, but let's keep this simple for the moment). Yes. Yes. SPC = Small Peripheral Controller. 'Normal' backplanes, meaning ones that weren't designed for specific multi-card peripherals (like the RK11-D, RK611) are all SPC slots. Yes. The SPC part is strictly the front 4 connectors only. The rear 2 connecotrs -- A and B -- are either MUD (Modified Unibus Device, used for some memory cards) or plain Unibus in/out, or even something stranger. The front 4 connectors of the last slot and first slot on your backplanes are part of the grant chain and need the continuity cards (and NPG jumpers) Yep, except of course you'd not do that. You'd pull the M920 jumper and put the terminator in the last slot of the CPU backplane. -tony

A very minor correction : I've got some 3rd party hex-height SPC cards (The interfacae for the I2S Model 70 image display, for example) that have a rectangular cutout where the A-B connectors would be. That will fit over an M920 jumper or M930 terminator (but not, of course, the longer M9302 terminator), so this card can go in the 'end' slot of a backplane. -tony

Careful: the M9312 is for the CPU end of the bus, and besides the near-end termination, it provides for diagnostic and boot ROMs, so it is *not* a replacement for the M9302, but it's counterpart for the other end of the bus. As such, the M9312 goes into a MUD slot (*modified* UNIBUS device), which has some pin designations differ from a *standard* UNIBUS slot, which is the reason why the regular terminator (M930 or M9302) needs to go into the last (=standard) slot, not anywhere in between. Hence, the M9312 (designed for MUD slots) must NOT go into the last slot for the same reason. Further, there are some (five? W1 through W5?) jumpers on the M9312 that connect pullup resistors to certain bus lines. There are CPUs for which the jumpers need to be in, other CPUs have equivalent resistors on the CPU boards, so the M9312 jumpers must be out for these. I don't have the details at hand, but can look them up if you don't find the manuals elsewhere. Another near-end terminator and ROM board would be the M9301, but this one doesn't have the pullup resistors. If the /44 needs external pullup, you would be bound to use the M9312. ROM chips are NOT interchangeable between the two boards. Guy Sotomayor wrote: ... -- Andreas Freiherr Vishay Semiconductor GmbH, Heilbronn, Germany http://www.vishay.com

Eric, you're right: I checked the manual again, and found that the M9312 is designed to work in either a standard Unibus or MUD slot. You only need to remove jumper W-6 for MUD operation (to keep the buffered "VECTOR L" signal away from the +5V battery backup power line). I was blinded because I had never seen this module used at the far end. In fact, if there is a bus repeater, the M9312 must be installed at the CPU side of the repeater (says the manual). In my 11/34A, leaving the M9312 at the CPU end makes connections to the front panel simpler: the other end of the bus is in an expansion box, separate from the box containing the CPU and the front panel. BTW, somebody asked for pictures a while ago. Please visit http://andreas.freiherr.bei.t-online.de/pdp-11/index.htm and have fun! Regards, Andreas Eric Smith wrote: ... -- Andreas Freiherr Vishay Semiconductor GmbH, Heilbronn, Germany http://www.vishay.com

On Thu, 2003-02-13 at 07:42, Ethan Dicks wrote: I thought the 11/45 was the second PDP-11 (and the first microcoded one). The 11/20 was the first and the *very* early ones just said PDP-11. When the 11/45 was introduced, it was re-named the 11/20. The 11/15 is an OEM version of the 11/20. Just like the 11/05 is the OEM version of the 11/10. I'm note sure which CPU has more cards, the 11/20 or the 11/45. :-) The 11/20 has *alot* of flip chips. That's what you get when you just use SSI TTL. The 11/45 atleast used MSI. -- TTFN - Guy

On Sat, 2003-02-15 at 16:08, Ethan Dicks wrote: My introduction to PDP-11s (and PDP-10s) was in school. The notable introductions while I was there were: 11/34, KL10, and the 11/780 (we had s/n 1). We had gobs of 11/40s and 11/20s (even had a few PDP-11s - no other designation ie early 11/20s). C. Gordon Bell had a chair in the EE department while I was there too (though you didn't see him much -- something about this computer company up in MA). BTW anyone know where I can find a set of manuals for BLISS-11? It's what I primarily programmed in (that and SAIL and eventually 'C') while in school. If I'm feeding the nostaliga bug, I might was well do the software as well as the hardware. -- TTFN - Guy

Andreas Freiherr wrote: Nice pictures, but your PDP-11 history isn't quite correct. The PDP-11 series actually started with ... the PDP-11 ... which was very quickly renamed the PDP-11/20. The 11/10 came along just a little bit later.

Anybody on the list have a copy of Fassbinder's "Welt am Draht" / "World on a Wire" that I can borrow for viewing? Alternately, have any of the Europeans on the list heard of plans to release this on DVD? Important and on topic since this may be the first occurrence of VR in film. John A.

John, the movie was on German TV years ago (rerun later, but also years ago already) in two parts. I have it on VHS tape, and I am lucky enough to have a printed listing so I don't need the broken RD53 in the PDP-11 to find the tape. However, I am not sure if this will really help you: it is in German, and it is in PAL video format, so you as well as your VCR will need special features to be able to understand it. ;-) Technical details are in http://uk.imdb.com/Title?0070904 - just in case you are only looking for these... A similar idea is behind "Matrix" and "The 13th Floor", but Fassbinder's version is indeed a classic and impressive one. Regards, Andreas John Allain wrote: -- Andreas Freiherr Vishay Semiconductor GmbH, Heilbronn, Germany http://www.vishay.com