Or even non-technical. I've constantly had a low level of cognitive dissonance when reading this thread, because to me ADF has another, much longer-standing, meaning: ?r nDra?ocht F?in. /~\ The ASCII der Mouse \ / Ribbon Campaign X Against HTML mouse(a)rodents.montreal.qc.ca / \ Email! 7D C8 61 52 5D E7 2D 39 4E F1 31 3E E8 B3 27 4B

So now that I've been properly informated that I can't have an 11/74, is there a resource anywhere of what parts will play together, and makes for a sensible workable system? I'm hoping someone has a good web page, or can reference a web-obtainable DEC document. 'cause I want to start shopping. And I still want a system that will support a front panel, in the end. --jc

jcwren wrote: If you want a PDP-11 with a "real" front panel (binary switches and lights), the choices are: PDP-11/05 (or OEM model, PDP-11/10) Small (CPU on two hex modules). Relatively slow. PDP-11/20 The original. Sometimes simply marked "PDP-11". The only PDP-11 that isn't microcoded. Lots of small cards. PDP-11/40 (or OEM model, PDP-11/35) Mid-range. PDP-11/45 (or OEM model, PDP-11/50) High end. Fast. PDP-11/55 Same CPU as 11/45, but with bipolar RAM. Very fast. PDP-11/70 PDP-11/45 CPU extended to support 22-bit addressing, 32-bit memory bus, cache, and Massbus peripherals. Very very fast (depending on cache hit ratio). If you will settle for the "calculator-style" front panel (octal keypad and LED display), there are three more choices: PDP-11/04 Low end, replacement for 11/05. PDP-11/34 Mid-range, replacment for 11/40. PDP-11/60 High end of mid-range. More microcode than any other non-VLSI PDP-11 model; only TTL-based PDP-11 that supported user-written microcde. If it had had 22-bit addressing, it might have been popular. The PDP-11/44 was the last of the TTL-based PDP-11 processors, but it used a microprocessor-based console, so there are no switches and blinkenlights. These systems were not all marketed concurrently, since they were designed at different times over more than a decade, so there isn't any single place where they are all described in detail. The information on supported configurations was found in the "PDP-11 Systems and Options Catalog", and in Software Product Descriptions (SPDs). Those are hard to find now, but the various PDP-11 Processor Handbooks and Peripheral Handbooks are easier to find and turn up on eBay from time to time. Some of the processor and system reference manuals are on www.bitsavers.org. I'll ignore Qbus for the remainder of this posting, because the PDP-11 models that have "real" front panels don't have Qbus. Normally Qbus is only found on some (but not all) of the VLSI-based PDP-11s, using the LSI-11, F-11, T-11, or J-11 chip sets. Able sold a "Qniverter" product that allowed the use of Qbus peripherals on a Unibus system, or vice versa, but these are not common. PDP-11 peripherals (and some of the memory) come in two main types, Unibus System Units and Small Peripheral Controllers (SPC). A System Unit is a collection of cards in a specially-wired 4-slot or 9-slot backplane. Be careful when buying modules that go in System Units; if you don't have the backplane, they're of no use. Examples of System Units are the RK11-D DECdisk control, RH11 Massbus adapter, and MM11-L core memory. SPCs are peripherals on a single quad or hex module. They need to go in an SPC slot in a backplane. The system or processor reference manuals explain which slots in the processor backplane are wired for SPCs. The DD11-CK and DD11-DK are 4-slot and 9-slot generic SPC backplanes, so if you don't have extra SPC slots in your processor backplane, you can use on of these. Also, so dedicated System Units have a few extra slots that can accept SPC modules. You have to be VERY careful about what slots you plug things into; slots for dedicated cards, SPC modules, Modified Unibus devices, etc. all physically look identical, but if you plug things into the wrong kind of slot, at best they don't work and damage to either the module or the system is possible. ALWAYS check the reference manuals if you aren't sure (and best to check even if you think you know it; From personal experience I can state that it's very easy to be wrong about these things). As a general rule, the Unibus is present on the A and B edges of the first and last slot of each backplane. (Only the last slot on some processor backplanes.) When you have multiple backplanes in one box, you connect them via M920 or M9202 jumpers. M920 are the short ones. M9202 are tall, and have a folded flat cable packed between the two connector modules. The M9202 is used to distribute the AC loading of the bus better. To connect backplanes between separate cabinets, you need BC11 cables. A few early peripherals, such as the TC11 DECtape control and RK11-C DECdisk control, have one or more 19" mounting panels full of modules. For these you have to check the docs to find out which backplane slots are for the Unibus In and Unibus Out cables. The Unibus-out slot of the last backplane *MUST* have a terminator. The M930 was at one time common, and is a really small card that's hard to get out of a full backplane. The M9302 is a tall card, and IIRC does a bit more than the M930. On more recent systems, the M9301 and M9312 are common, and combine the terminator with bootstrap PROMs. SPC modules use signals on the C, D, E, and F edges. SPC modules come in quad and hex height. Hex height SPC cards normally do not use anything from the A and B edges other than power. The A and B edges of slots intended for SPC cards sometimes are wired for Modified Unibus Devices (MUDs). Be careful not to plug a MUD device into a standard Unibus slot or vice versa. The only MUD devices I know about are memory cards, but perhaps there are others. There are also "Extended Unibus" slots in the PDP-11/24 and PDP-11/44, which have extra memory address lines. Once again, be very careful how you use those slots. Since all of the PDP-11 systems with "real" front panels used Unibus, you can generally use almost any Unibus or SPC peripherals on any of the CPUs. Memory is a little bit trickier; the high-end CPUs like the 11/45 and 11/70 require special memory. The 11/20 uses Unibus memory, but it uses different backplanes and power harnesses than anything else, so most of the Unibus core memory System Units cannot be used in the 11/20 chassis, though they will work fine with the 11/20 if installed in an expander. Hopefully this has given you some idea of what you're getting into. It probably sounds complicated, and I've deliberately emphasized some of the areas in which you can get into trouble, but it's really not that bad as long as you read the documentation. When in doubt, ask here or over in alt.sys.pdp11. Eric Smith [ClassicCmp posting copyright 2003 Eric Smith. Not to be redistributed without permission of the author.]

[...] If you're a sufficiently dedicated (read : Mad) hacker you can always wire-wrap your own special backplanes for boards that need them. It's quite a bit of work (I did one over a long weekend...) but it is possible. Strictly yuo need a terminator at _each_ end of the Unibus. In the case of the 11/45, you put an M930 card in the top front slot of the CPU It provides an SACK signal if a grant gets to the terminator (this will mean very little unless you've seriously hacked about with the Unibus). This is a Good Thing under normal circumstances, but a Bad Thing if the grant chain is open for any reason (missing grant continuity card or jumper) -- it locks up the entire machine as the arbiter tries to remove the grant (which it can't do, since it's not coming from the arbiter due to the open grant chain) and thus release the SACK. It's handy to have an M930 around for testing -- stick that in place of the M9302 and see if the machine will at least do something. If so, you can then start looking for grant chain problems. backplane (CPU end terminator) and one in the Unibus Out slot of the last backplane on the bus. Often (certianly in machines like the 11/34) you put the terminator-with-boot-ROMs in the CPU-end termiator position (often in a dedicated slot in the CPU backplane). You then put an M9302 (or an M930, I suppose) in the Unibus Out of the last backplane. THey're basically MUS slots with the extr address lines IIRC. Not so in the case of the 11/45. You can use normal Unibus memory cards on that machine, although you need to put them in an MUD slot in an expansion backplane, not in the memory slots on the CPU backplane. You can also use the core-based system units. An 11/45 configured this way will not give the same performance as one with the speical high-speed memory, but it certainly will run, and run correctly. -tony

You are limited to 124K words of memory on the Unibus. On the 11/45 that's all the memory the machine can address, and yes, you can have it all on the Unibus. On the 11/70, that's only a small fraction of the address space. It seems perverse to have a CPU capable of 22 bit addressing, and with fast Massbus interfaces, and then cripple it like this! I suspect you can use Unibus memory on the 11/44 too, with similar restrictions. -tony