Plessy core memory

[Nigel Johnson Ham]

I'm sorry, on the memories, I went to look at my old notebook form that 
era, but it seems some pages have fallen out over time :-)

I think a friend has an 11/05 or 10, I will ask him for its 
configuration and see if that will help.

cheers,

Nigel


Nigel Johnson, MSc., MIEEE, MCSE VE3ID/G4AJQ/VA3MCU
Amateur Radio, the origin of the open-source concept!
Skype:  TILBURY2591nw.johnson at ieee.org



On 2022-01-09 19:57, Chris Zach via cctalk wrote:
> Probably. It's a 1973 version, the DD11-B is a MUD backplane, but it 
> seems to only have power plugs for +5,+15,-15. Looking at the MUD 
> specs I see there are backplane pins assigned for +20 and -5 so I 
> might be able to cobble something together.
>
> That's one of the fun things about Unibus: There were so many 
> different types that there was no guarantee that anything would work 
> in anything. I know this one worked with an RX11 because that's what I 
> used 30 years ago. Would it work with an RX21? Maybe. Maybe not.
>
> Note: I did check the DD11 and sure enough all of the DMA grant wires 
> are factory jumpered. I did remove the wire from one of them so I can 
> use either a RL11 or an RX21 but in the meantime I have a G7273 in 
> there along with the knucklebusters in the other slots)
>
> Getting this MM11-DP to work might take a fair bit of thought. I'm 
> guessing that the DD11-F is significantly different from the DD11-B?
>
> And the big question: What memories (if any) will work in a DD11-B 
> equipped pdp11/10?
>
> C
>
> On 1/9/2022 5:48 PM, Nigel Johnson Ham via cctalk wrote:
>> I would assume that your 11/10 has the suffix -NC.  There were two 
>> versions, the -NC used -15V four wire memory, and the later -SC used 
>> +20V three-wire memory.
>>
>> The +20V was provided by a MUD slot (Modified Unibus Device) and 
>> there was usually a big red sticker in it warning to not plug a 
>> module in that was not wired for it.
>>
>> I believe it was standard in all models after the second version of 
>> the 11/05 -/10
>>
>> I once tried to fix an 11/34 off-contract that somebody had done 
>> exactly that to- I gave up when I found that the +20V had been routed 
>> to some unobtainable ROMs on the CPU board.
>>
>> cheers,
>>
>> Nigel
>>
>>
>> Nigel Johnson, MSc., MIEEE, MCSE VE3ID/G4AJQ/VA3MCU
>> Amateur Radio, the origin of the open-source concept!
>> Skype: TILBURY2591nw.johnson at ieee.org
>>
>>
>>
>> On 2022-01-09 17:04, Chris Zach via cctalk wrote:
>>> I'm working on my pdp11/10 getting it back together. One problem I 
>>> think I have is that the secondary memory (a Plessy 700101-100) may 
>>> be shorting the -15 line for some reason. Working on it, but does 
>>> anyone have a manual or anything like that for this kind of memory 
>>> board?
>>>
>>> Alternately, what kind of Unibus 16k memory board exists to get a 
>>> 11/10 from 16kw to 32kw of memory? Apparently I can't use a MM11-B 
>>> as it requires +20 and -5, both of which are not provided by the 
>>> power supply or sourced on a DD11-B backplane module. The 11/10 has 
>>> +15, -15, and +5.
>>>
>>> On a related note, where did +20 come from for Unibus and which 
>>> systems even supported it? Was it an 11/45,11/70 thing?
>>>
>>> Thoughts?
>>> C
>>>
>>> (Yes, I could build a regulator to take the 30 volts between +15 and 
>>> -15 and create an independent 20 volts. Maybe. Likewise I could 
>>> generate -5 from the -15 and a 7815 regulator. Maybe.)