At present PDP-11 computer systems are mostly forgotten, but there are PDP-11 compatible Soviet microprocessors still available on eBay (never used "new old stock") as KR1801VM2 (КР1801ВМ2 in Russian) and I'm going to bring PDP-11 of some sort back - I'm designing an open source computer (licensed under CERN OHL v1.2) around that chip (VM2 was 2nd version of Soviet single chip implementation of LSI-11 system [ not a clone!!! ] which could be used to build PDP-11/03 kind of machine) with open source modules and backplane in mini-ITX form factor 170*170mm (see GitLab) that could fit into regular mini-ITX computer case (that is cheap) to make a true 16-bit modern retro computer with PS/2 keyboard (and may be mouse) and connected to [S]VGA monitor:

As you can see design is inspired by famous RC2014 ;)

UPDATE1: On April 26th this project was featured on hackaday.com :)
https://hackaday.com/2018/04/26/a-mini-itx-pdp-11/

UPDATE2: Mailing list for all nedoPC projects in English: 

https://groups.google.com/d/forum/nedopc

http://groups.google.com/group/nedopc (old link)


Mini-ITX spec with all sizes could be found here

I didn't want to use Q-bus (called "LSI-11 bus" in earlier DEC documentation) as is (in it's original edge-connector form) because it's huge and almost half of contacts are not used, so I put all meaningful signals of Q-bus in 1-row header (slightly re-arranged) and in the same row (after 1 missed pin) I added all other signals from VM2 microprocessor and also de-multiplexed and inverted address lines - there are no modern ICs that could decode multiplexed Q-bus with proper handshaking natively (except for some number of old Soviet memory chips that mostly defective) so presence of already demultiplexed and inverted address will help to connect regular memory RAM and ROM chips. So it's 62-pin header (37th pin is missing) that could fit in 6.3 inches ( or 160mm that is coincidentally a limit for Eagle v5 Standard Edition that I own since 2007 ; ) and collectively I call this interface "Bread-Board friendly Q-bus extended" or BBQ-bus+ :)

PositionName (bold if Q-bus)
Where connected
1GNDGround - pin 1 and 20 of VM2
2BDMR L/DMR - pin 12 of VM2
3BSACK L/SACK - pin 13 of VM2
4BDMGI LDaisy chained BDMGO
5
BDMGO L /DMGO - pin 14 of VM2
6BHALT L/HALT - pin 29 of VM2
7BDCOK H/DCLO - pin 26 of VM2
8BPOK H/ACLO - pin 25 of VM2
9BINIT L/INIT - pin 27 of VM2
10BEVENT L/EVNT - pin 30 of VM2
11BIRQ4 L/VIRQ - pin 28 of VM2
12BIAKI LDaisy chained BIAKO
13BIAKO L
/IAKO - pin 24 of VM2
14BDIN L/DIN - pin 22 of VM2
15BDOUT L/DOUT - pin 18 of VM2
16BRPLY L/RPLY - pin 17 of VM2
17BSYNC L/SYNC - pin 21 of VM2
18BWTBT L/WTBT - pin 19 of VM2
19BBS7 LLogical 0 if A15=A14=A13=1
20BDAL0 L/AD0 - pin 9 of VM2
21BDAL1 L/AD1 - pin 8 of VM2
22BDAL2 L/AD2 - pin 7 of VM2
23BDAL3 L/AD3 - pin 6 of VM2
24BDAL4 L/AD4 - pin 5 of VM2
25BDAL5 L/AD5 - pin 4 of VM2
26BDAL6 L/AD6 - pin 3 of VM2
27BDAL7 L/AD7 - pin 2 of VM2
28BDAL8 L/AD8 - pin 39 of VM2
29BDAL9 L/AD9 - pin 38 of VM2
30BDAL10 L/AD10 - pin 37 of VM2
31BDAL11 L/AD11 - pin 36 of VM2
32BDAL12 L/AD12 - pin 35 of VM2
33BDAL13 L/AD13 - pin 34 of VM2
34BDAL14 L/AD14 - pin 33 of VM2
35BDAL15 L/AD15 - pin 32 of VM2
36PWR5V+5V (switchable) - pin 40 of VM2
37
NOT CONNECTED (a key)
38CLCICLCI - pin 16 of VM2
39CLCOCLCO - pin 15 of VM2
40A0Latched inverted /AD0
41A1Latched inverted /AD1
42A2Latched inverted /AD2
43A3Latched inverted /AD3
44A4Latched inverted /AD4
45A5Latched inverted /AD5
46A6Latched inverted /AD6
47A7Latched inverted /AD7
48A8Latched inverted /AD8
49A9Latched inverted /AD9
50A10Latched inverted /AD10
51A11Latched inverted /AD11
52A12Latched inverted /AD12
53A13Latched inverted /AD13
54A14Latched inverted /AD14
55A15Latched inverted /AD15
56A16*
Inverted /SEL - pin 31 of VM2
57SPARE1/WRQ - pin 10 of VM2 (pulled up)
58SPARE2/WAKI - pin 11 of VM2 (grounded)
59SPARE3/AR - pin 23 (wired to /SYNC)
60SPARE4
61SPARE5
62SPARE6Main +5V (permanent)