On 01/11/2019 02:32 PM, Noel Chiappa via cctalk wrote: > > From: Allison Parent > > > Most Probable cause is interrupt grant is broken. > > The only -11 that complains if the grant chain is broken that I know of is > the /34 (maybe the /04 too). I certainly have a QBUS chassis right next to my > workstation here that i) has a bunch of empty slots, and ii) works fine, as > long as there are no empty slots between the CPU and the devices. I'm far from a newby to Qbus 11s as I stated with LSI-11 nearly 4 decades ago and I ahve all Qbus models of note from LSI-11(quad), 11/2 (dual) , 11/23(dual) 11/23(quad), 11/23B(quad), 11/73(dual) in various BA11VA, BA-11s, BA11N, BA23, BA123, and also microVAXII in BA23 and BA123. Which covers about eight different Qbus backplane variations not including the Heath H11 and a engineering one off (8 slot dual width with bigger supply sorta like taller a BA11VA 4 slot. Small advantage to being a Millrat. I forgo most non-Qbus 11s to specialize.
All of my 11s are Qbus and yes they complain if the interrupt grant chain is broken. Missing CSR is the usual complaint. Typical micorpdp-11 Qbus is: First three slots after CPU the CD slots are open use, or be used or memory private bus. ABCD CPU ABCD where CD is memory wired not bus ABCD ABCD up to this slot memory does not have to grant interrupts on the right (CD)side of quad cards ABAB All cards dual or quad must have int grant jumper of the board or grant card. ABAB ABAB ABAB > Also, IIRC he said it works with 3 cards plugged in, but not 4; how can > plugging a card _in_ cause grant problems? See the above... Qbus is can or cannot be uniform for quad or dual width cards. For most only bus slots that are AB bussed are data/address. But they can be serpentine for quad wide systems and most quad wide board have interrupt grant jumpers on the board or are just hardwired that way. Qbus is not Unibus. You can build a Qbus system of all dual width cards, some Qbus system memory uses PMI. For example I have an 11/23b+ in a quad width BA11-N but the backplane is nonstandard ,18 slots of Q22 ABAB (serpentine wired). It has a quad width 11/23B and 8 MSV11 256KB dual width Q22 memory. RQDX3 dual width, RXV21 RX02, DRV11J and a M7555 (also found in MicroVAXII in BA123 boxes, takes the 50pin wide RQDX breaks it out for multiple RX33 floppy and RD32 drives). There are many Qbus backplanes and several different configurations for DUAL/QUAD mixes of cards. The Microvax Qbus backplanes also fit in that realm such as BA123 with J11 cpus installed and PMI ram. Also many of the Qbus can be Q16(not many), Q18(fairly common) and Q22(only late and MicroVax) address bus width. The microcomputers handbook is a start and the modules manuals. Typically you need a 1980 version and a later 80s versions. Also the LSI-11 Systems Service Manual Volumes 1 and 2. Generally the more docs you have for Qbus 11 systems and the MicroVAX kin the less pain you will have configuring them especially for non standard configurations or systems with mix and match boards. Allison