PDP-11 Memory

[Jerry Weiss]

On 1/11/19 11:28 AM, Bill Gunshannon via cctalk 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?
1) You might want to check your power supply loading.   You have a lot 
of memory of chips to feed.   The H7864 output at +5V is 36 amps.  
Between the KDJ11-B and 4 memory boards you may be using between 20-25 
amps. Add a  disk controller, disk drive and any other Q-bus devices 
might bring you close to the limits for either +5V or +12V from an aging 
supply.

2) Are the CSR addresses between 17772100-06?  Have you tried to move 
them above this range just to see if the behavior changes?

   Jerry