PDP-11 Memory

[Bill Gunshannon]

On 1/11/19 3:34 PM, Jerry Weiss wrote:
> 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.

Nothing but CPU and memory at this point.  And there will never be
drives as I will be using SCSI and 6 of them sit in a box of their
own just waiting for the PDP-11 to wake up and smell the coffee.

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

CSR's are right.  As I said, the combo worked until I moved it
to a different backplane.  I think Allison has the idea. I am
going to go back and look into bus grants.  But I would have
thought they would be alright as the likelihood of these being
in a serpentine A-B box seems much to likely for them to not
be capable of it.

bill