Plessy core memory
Nigel Johnson Ham
g4ajq1 at gmail.com
Sun Jan 9 19:00:37 CST 2022
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.
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?
> 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.
>> 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
>>> 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?
>>> (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.)
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