PDP-11 Memory

[Bill Gunshannon]

On 1/11/19 2:25 PM, Allison Parent via cctalk wrote:
> Most Probable cause is interrupt grant is broken.  For most microspheres backplanes the first three slots are different than remaining.

Yes, that's true.  But the problem doesn't occur until the 5th slot.
And a quick look at the C-D edges of the board shows that the BUS
Grant lines are jumpered. So the 2 A-B slots should pass the grants
just fine. I saw  no mention about these not working in A-B/A-B
backplanes.  The only mention the docs make at all is that the
only lines used on C-D slots is power.

bill



> 
> 
> Phoned this in!
> 
> 
> On Jan 11, 2019, at 12:28 PM, Bill Gunshannon via cctalk <cctalk at classiccmp.org> wrote:
> 
> 
> Well, it has been so long since I had to put together an
> entire system I forgot what fun it can be.
> 
> With almost documentation I was able to configure 4 1meg
> memory modules and I tested them all in my 11/23+ box.
> 
> 
> KDJ11-B with 4 different (but similar) memory cards.
> "MAP" option of the KDJ11 shows 4 meg (minus the I/O
> Page) and all the right CSR's for the first four blocks.
> 
> Really wanted to make this a deskside so I moved the
> cards to a MicroPDP box (Yes, I have a coule of the
> deskside pedestals).  Power on, Memory CSR error.
> Move then back to the 11/23+ works fine.  If I only
> put the first three in the MicroPDP box it works.
> But as soon as I try to put in a fourth module I
> get the memory CSR error.  Tried different cards
> (although working in the 11/23+ box would make me
> think it is not a problem with the card) no help.
> 
> Anybody care to take a stab at what might be causing
> this problem?
> 
> bill
>