In short the LSIbox is a small-DEC like case with a visible LSI-11 card cage on top and a "BeagleBone" micro-Linux system inside to operate the PDP-11.


  • makes a cool presentation of a running DEC QBUS system.
  • is a perfect PDP-11 development platform.
  • fits onto a crowded programmers desktop or into economy flight class baggage.


lsibox single


lsibox back

This is of courses a variation of the DECbox theme: wonderful vintage devices, supported by well-hidden 21th century electronics.

Among other things, LSIbox is also a complete Linux PC:

lsibox fan kbd monitor

"WELCOME TO ADVENTURE!" Bring a HDMI cable for the television set, and you can play on a real PDP-11 in every hotel room.



While current activity of these retro-guys (me included!) seems to build replacements and simulation of DEC equipment as crazy, LSIbox is intended to highlight the original DEC hardware, (lift it on a throne, show it to the world), while all the modern stuff is well-hidden.

This picture was one inspiration:

LSI 11, PDP 11 03 User's Manual (May 1976, EK LSI11 TM 003) 1


LSIbox should look like these pseudo-retro tube amplifiers: Vintage electronic proudly shown, embedded in modern environment.


The Mac Mini was also in my mind ... but surely my crafting skills can't compare with Apple's (but DEC quality is easier to reach ;-)




Feature creep?

I tried to build every imaginable feature into the LSIbox, while maintaining a clean outfit. Should be a "power box"!

The LSIbox project is build around the wonderful compact H9270 LSI-11/03 QBUS backplane.
It has 8 dual-slots and can carry all CPUs: LSI-11/03 and LSI-11/2, 11/23 with F11-chipset and 11/73 with J11 chip.
Additional RAM and a DLV serial card make a minimal system (not even ROMs required).
Drive and network controllers can be added, but "driveless" operation is possible.

  • To keep the system clean like a gem, instead of bulky disk drives a SCSI controller with SCS2ID card emulates a lot of disks and hosts some operating systems.
  • An BeagleBone Black ("BBB") is squeezed into the case. It acts as a front end processor to the LSI system.
  • To hide cables, 4 RS232 and a DEQNA network connectors are routed through the case.
  • An original 11/03 panel is build into the case and has all functions: Power ON/Off, HALT/RUN and RESTART.
  • A crystal-stabilized 50Hz clock signal for the LSI-11 LTC (line time clock) is embedded.
  • Ethernet connection allows remote control of the whole LSIbox.
  • The BeagleBone runs Debian. Debian shows a desktop, a monitor plugs into a HDMI connector, and a wireless keyboard/mouse can be connected to an USB port.
    But if not on a show, remote operation over ssh connections will do.
  • GPIO signals hook-in between panel and QBUS backplane, so all panel functions can be initiated from Linux shell too. This allows for total remote control of the PDP-11.
    (includes HALT/RUN/RESET, switching of an extra LED in the panel, and enable/disable of the LTC signal).
  • A "BlinkenCape" exposes 4 BeagleBone UARTs.
  • Two of the 4 LSI PDP-11 SLU connectors can be connected to two BBB UARTs by switching internal signal relays.
    So two Linux UARTs are connected to two LSI11 SLU's over switchable internal null modem cables.
    The switchable ports normally are the PDP-11 console at 177560 and the TU58 port at 176500.
    A red LED between associated BBB and PDP-11 ports indicates "internal connection".

lsibox back detail

  • Since BBB software has access to PDP-11 serial console, code can be downloaded and started over ODT console commands. This includes bootloaders for all possible disks and tapes, so the PDP-11 needs no BOOT ROM card.
  • The PDP-11 can be operated "driveless", BBB providing a TU58 emulation with "tu58fs". Full XXDP and RT-11 installations can be booted.
  • Finally a PC power supply powers all this stuff. It can deliver 250 watts with 15 Amps of 5V, which is really necessary for all planned QBUS cards. It also generates air flow through the box.
  • For cooling a separate stand-alone fan unit was designed.
  • And operation is only allowed with the white, round-edged wireless Logitech K400 keyboard/mouse in same optical style.

 lsibox fan kbd only