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 FORTRAN is set FORTRA 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) LD DL VM SP BA NL 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.]