Next project: 11/24. Does it need memory?

Chris Zach cz at
Mon Oct 19 21:47:26 CDT 2020

Indeed. I had it running 30 years ago, it was my RX01 floppy pdp11. 
Unfortunately I think I removed, gave away, or something-ed one of the 
Plessy core memory boards. Which means I can't just boot it and continue 
where I left off (I seem to recall it ran Dungeon off RX01's).

The 11/05 has memory boards as follows:

M930/H214 (begin terminator, core plane)
Unibus jumper/H214 (end of line)

It does not have the KW11 line time clock or the weird serial port that 
could be run off the CPU. Instead a normal boring DL11.

So 2 MM11-L's for 16kw of memory. Why do I have an extra H216 core board 
lying around. Anyone got an extra 4k of memory lying around?

Hm. I guess I could put my DA11-F Unibus window in there and jumper it 
so that a 4k window of memory on the 11/24 appears on the 11/05. That 
could work, unless someone has a spare 4/8kw of core they don't need.

The Plessy board is stuck in there tight with no easy way to remove. It 
says its an 8k*16 PM1105. Crap, it might be jumpered for the last 8k. 
But that does mean I swapped a core board. You know I might have traded 
it to MG in return for a pair of Sun386i's for CrystelCom's mail and DNS 
servers. Maybe if he still has it I can trade it for this 216 core plane 
if he just wants one on his wall.


On 10/19/2020 8:25 PM, Guy Sotomayor wrote:
> On Mon, 2020-10-19 at 20:20 -0400, Chris Zach via cctalk wrote:
>> won't work. Maybe I'll just drag out the 11/05 and get that working
>> first, it's got a nice front panel that doesn't lock up often :-)
> The 11/05 was the first 11 that I repaired and got working.  You should
> note that the 11/05's front panel is driven by the uCode of the CPU.
> It's connection to the CPU is through a "serial" protocol (it's been
> too long...I think it's just a big shift register) to keep the pin
> count (e.g. cost) low.
> TTFN - Guy

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