On Tue, Jun 15, 2021 at 4:47 PM Tom Uban <[email protected]> wrote: > > On 6/15/21 8:58 AM, Tony Duell via cctalk wrote: > > On Tue, Jun 15, 2021 at 6:34 AM Tom Uban via cctalk > > <[email protected]> wrote: > > > >> My KM11s are based on Tony Duell's schematic and if you look, switches S3 > >> and S4 are both driving outputs rather than simply switching them to > >> ground, > >> so I don't think two boards at one time would work if these signals are > >> simply > >> tied in parallel on slots A2 and B2. > > I took the switch circuits from the offical KM11 schematics which are > > either in the PDP11/45 CPU printset or the RK11-C printset that I > > have, I forget which. I certainly didn't add logic or replace > > open-collector parts with totem-pole ones. > > > > -tony > I did not mean to imply that you had changed the behavior in your KM11 design. > You are surely a competent and trusted pdp11 resource :) >
I didn't mean to imply anythimg like that either. I was just confirming that my KM11-a-like and a real one will behave the same way, so if my version can't be used in pairs in an11/05, then the real one can't either.. I've been involved with classic computers for long enough to know that sometimes clones are not exactly identical to the real thing. I do have a pair of real KM11s now. Each is a pair of boards that plug together. The board that goes into the machine's backplane is discrete transistor lamp drivers, the one that plugs into it (and thus sticks out of the cardcage) contains the lamps, switches and ICs for the switch circuitry. I know where they are if you want me to confirm the IC numbers or whatever. -tony
