pdp11/84 PMI memory: What is the problem with Q bus?

Chris Zach cz at alembic.crystel.com
Sun Apr 19 14:29:44 CDT 2020

So I picked up an 11/84 CPU, 3mb of memory, and a 11/84 Unibus card on 
Ebay. Goal is to speed up my fastest 11 here

For boot time, the diagnostics run in 13 seconds (from when it starts to 
prompt) on the 11/73 board I have and 13 seconds on the 11/84 board. 
This is with a camintonn 2mb half height memory board.

Put in the first PMI module above the 11/84 CPU and tried it out. This 
is a CA rev board which apparently only works in a Unibus pdp11 and not 
a Q-bus one. Apparently it does work.

So what exactly was the bug with the older PMI memory? Block mode DMA, 
I'm using an MTI ESDI controller which can do 16 word block DMA on Q 
Bus. Something else?

Here's the output from RT11.

.show all

RT-11FB (S) V05.05
Booted from DU6:RT11FB

USR     is set SWAP
EXIT    is set SWAP
KMON    is set NOIND
TT      is set NOQUIET
ERROR   is set ERROR
SL      is set OFF
EDIT    is set KED
KMON nesting depth is 3
Global .SCCA flag is disabled

PDP 11/83 Processor
2048KB of memory
Floating Point Accelerator Unit
Extended Instruction Set (EIS)
Memory Management Unit
ECC Memory
Cache Memory
PMI Memory
60 Cycle System Clock

Device I/O time-out support
Error logging support
Memory parity support
System job support
Global .SCCA support
FPU support
Extended unit support

Device    Status                   CSR     Vector(s)
------    ------                   ---     ---------
   EL      Not installed           000000   000
   LD      Installed               000000   000
   BA      Installed               000000   000
   DY      Not installed           177170   264
   VM      Installed               177572   250
   SP      Installed               000000   110
   XL      Not installed           176500   300 304
   DL      Installed               174400   160
   MS      Not installed           172522   224
   DU      Resident                172150   154
   LS      Not installed           176510   310 314
   NL      Installed               000000   000

TT  (Resident)
DU  (Resident)
     DU6 = DK , SY
MQ  (Resident)
9 free slots

Job  Name  Console Level State    Low    High  Impure
---  ----  ------- ----- -----    ---    ----  ------
  0   RESORC   0      0   Run     000000 103232 105046

No multi-terminal support

Address   Module    Words
-------   ------    -----
160000    IOPAGE     4096.
132174    DU         5570.
103274    RMON       5856.
001000    ..BG..    16990.

LD0 is  DU6:RTTST.DSK[6000.]

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