Rod Smallwood rodsmallwood52 at btinternet.com
Wed Jun 1 13:05:23 CDT 2016

On 01/06/2016 18:50, Henk Gooijen wrote:
> -----Oorspronkelijk bericht----- From: Noel Chiappa Sent: Wednesday, 
> June 01, 2016 7:24 PM To: cctalk at classiccmp.org Cc: 
> jnc at mercury.lcs.mit.edu Subject: Re: PDP-11/94-E
>    > From: Henk Gooijen
>    > The first 4 (5?) slots are QBUS
> Technically, PMI, which is more-or-less QBUS on the left (A/B) side 
> (modulo
> not having grants, unless the appropriate backplane jumpers are set to 
> send
> grants to those slots), and it uses the standard CD interconnect (as 
> in Q/CD
> backplanes) on the right (C/D) side to carry PMI.
>    > The RX211 must have the NPR/NPG open. Check the documention which 
>    > switch must be set in the correct position. However, not sure if 
> that
>    > would cause the RX211 to be "invisible".
> Right; DMA would not work, but normal master/slave UNIBUS read/write 
> cycles
> to the device registers should still work.
> Noel
> ---------
> You can of course read and write the CSR and all other registers of 
> the RX211,
You could if you were able to get into ODT.  I have yet to discover how 
you get there.
> *if* it is in the memory space where you expect it. Making sure is 
> easy: check
> the jumpers / DIP switches on the RX211.
> Note that the RX11 (for RX01 drives) does *not* use DMA, and what's worse
> (IIRC) that module does NOT jumper CA1-CB1 on the module itself!
> The RX211 does use DMA, so the NPG should be open. As said, there is no
> need to cut the NPR/NPG wire, because those two pins  go to that first 
> module
> at the right side, and has a DIP switch to open / close the NPR/NPG 
> for *all*
> UNIBUS slots).
> But this is all from memory ... you can read the manual from bitsavers 
> too ;-)
> BTW, yes I have an 84 and an 94 in that box (power supply at the right 
> side
> of the box). Very similar in all aspects.  In fact, DEC did "rebrand" 
> an 84 to
> an 94 by swapping the CPU module (and removing the memory modules),
> and glueing a label saying PDP-11/94 over the original panel's PDP-11/84.
> I have such a box too. Hmmm, should take a picture of that ...
> - Henk

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