Qbus identification

On 04/04/2013 13:51, David Riley wrote: [ ... ] Indeed, or as Jerome suggested, looking at the configuration of the cards may give you a clue. So would the type of box: if it's a 3U-high (5.25") grey-fronted-metal-panel rack-mount box with three toggle switches, it's a BA11-N or BA11-S, which have straight backplanes (and are all QQ-CD), if it's a small tabletop box or a 2U (3.5") it's a BA11-V (tabletop) or BA11-M (2U) which have serpentine backplanes, and if it's a floor-standing microPDP-11 (or microVAX) box or a chassis with four or six pushbuttons on the front, it's a BA23 box which is QQ-CD in the top slots and serpentine below. Or count the card slots. All 9-slot backplanes are straight. 8-slot and 13-slot are mixed (for microPDP-11 and microVAX). Anything else is serpentine. BA11-M and BA11-V boxes are relatively uncommon. If it's a BA11-N, although the backplane is 18-bit, it's very easy to upgrade to 22-bit. All Q-Q backplanes are serpentine, and all straight backplanes are QQ-CD. The only odd one is the hex-high DDV11-B, which is a serpentine backplane in the ABCD positions and not bussed at all (except for power in the standard contact positions) in EF - it's meant for custom wiring. Of course we're assuming it's a DEC box with a DEC backplane. A Plessey backplane, for example, might be different, but you'd probably know if it was non-DEC, because it's pretty rare to find DEC's dark green connectors on anything non-DEC. Plessey and GEC ones, again for example, are white. -- Pete Peter Turnbull Network Manager University of York