Rebuilding a Sun 2/120

What would you do if you were to cross paths with the slaughtered remains of a Sun 2/120?

For me, the answer was simple: emergency resuscitation of course!

The poor beast consisted of merely the skeleton: the card cage and backplane, the cables and panel connectors, and the power supply and harness.

What I have acquired so far:

  • Sun 2/120 power supply (huge Boschert XL750-3626R 1200W!)
  • Card cage (9 slots)
  • Multibus backplane (Sun 501-1090)
  • Sun 2 CPU card, ROM Rev R (Sun 501-1007)
  • Sun 2 CPU card, ROM Rev R (Sun 501-1051)
  • Sun 1MiB RAM card (Sun 501-1048)
  • Sun 10MBit/s ethernet card (Sun 501-1004)
  • Sun bwone monochrome video card (Sun 501-1003)
  • Xylogics 450 SMD card (Sun 370-1012)
  • Xylogics 472 9-track pertec tape card (Sun 370-1067)
  • Serial port panel and cable
  • Ethernet panel and cable
  • Video + keyboard & mouse port panel and cable
  • SMD hard drive (Fujitsu M2322K via Arraid AEM-1)
    • SCSI emulator for CF-cards
  • SunOS 3.5 on five QIC-11 tapes.

What’s missing:

  • The beautiful chassis, I so desire this!! 🙁
  • SMD cables
  • More memory cards
  • Multibus SCSI card (Sun 501-1006)
  • Sun type-2 keyboard and mouse

Hopefully I’ve got an Intel Ethernet (Sun 501-1004) network card coming in soon-ish *fingers crossed*

The plan

Thanks to an opportunity at work, I managed to get a hold of two Arraid AEM-1 SMD emulators, one of which I could trade with a fellow retro Sun enthusiast for two CPU cards and a 1MiB memory card so my Sun 2/120 project suddenly looks very viable, without having to resort to cloning! Although I’m still considering making a 4MiB RAM card, because although originally standard, 1MiB is pretty tight.
I would certainly like to acquire a proper Sun 2/120 deskside chassis, but I’m considering re-purposing a large PC tower case meanwhile.



Finally started doing something, prompted by my SCSI CF emulator arriving. First stop is trying to get the power supply up and running again. Managed to resolder the jumpers from 110V to 220V and figuring out how everything is to be connected, in the process realizing a fuseholder (and fuse) is missing, so getting a replacement tomorrow.


Programmed two 27C128 EPROMs with Rev R bootprom images.


First test run of the PSU with no load. The two 5V rails measure fine, but the +12V, -12V, and -5V measure very low (+-1V.) I hope it’s because there is no load connected.


Connected the PSU to the card cage with the 501-1007 CPU card, the 501-1048 memory card, and the 501-1003 video card inserted. No chassis, so all spread out on the floor. Serial cable with null modem connected to my workstation, 9600bps 8N1.

Power on and…all 8 LEDs on the CPU light up and…stay lit…and…nothing…


At least all the PSU rails now measure properly, but what’s going on?

Out of the blue I think of swapping sockets of the two 27C128 EPROMs, and…

Sun Workstation, Model Sun-2/120 or Sun-2/170, Sun-2 keyboard
ROM Rev R, 1MB memory installed
Serial #7524, Ethernet address: 8:0:20:1:18:6

Probing Multibus:
Using RS232 A input.
Auto-boot in progress…
No default boot devices

Oh, yeah! We’re in business, big endian confusion be damned!


Placed orders for some 28AWG 60-way and 26-way cables, the corresponding IDC connectors, as well as an el cheapo IDC crimp tool, preparing to make me some SMD cables.


Figured out how to set up the Arraid AEM-1 to emulate a Fujitsu 2322K hard drive. Now I just have to wait for my SMD cables and my ethernet card to arrive before I can continue testing…


What looks like a NOS Sun 501-1004 ethernet card arrived at my doorstep today! Packaged inside a Multibus to VME adapter, but I’ve since released it from its prison, and put it in its proper cage.


Hopefully getting a 1/2″ 9-track tape multibus interface card in a few weeks. Could help with OS installations.


Xylogics 472 Pertec tape multibus interface card arrived. Unfortunately, probing the multibus either hangs or fails to find it. I’ve double checked the configuration jumpers and they appear to be correct. Could the EPROM have failed?


I received five QIC-11 tapes containing SunOS 3.5 for 68010! I doubt I will actually use these (probably not even readable anymore) but great for posterity!


Very long break, but finally cramming in some Sun restoration before the new year: made use of the IDC crimp tool, some cables, and some connectors so now I have an SMD control cable (60-pin) and an SMD data cable (26-pin.) Also starting to repurpose a large PC fulltower case to hold all the components. Looking good so far, I think I will be able to fit everything in a semi-decent manner. I ought to be able to run the 140mm and 200mm fans builtin to the case from the Boschert power supply. Finally starting to make a video cable to hookup to an RGB interface to hopefully get me some video so that no longer have to be content with just the serial connection.


  • The PSU must be switched from 115V to 230V and tested.
  • The CPU cards are missing bootproms. This one is easy to fix, I just need burn two 27C256 EPROMs with a bootprom image, luckily I have one.
  • The 501-1003 bwone framebuffer only outputs TTL levels and I don’t have a compatible monitor. I must figure out a way to convert the signal to display on a more modern monitor.
  • I need to figure out how to operate the Arraid to get the emulator set up. Serial command line interface is not so obvious.
  • I need to figure out how to do a network install. Will NetBSD with ndbootd be enough?
  • I don’t have a Sun type 2 keyboard/mouse; later models are electrically compatible but the connectors are different (RJ-11) so I’ll need to make an adapter. I think there was an official adapter for the DB-15 type 3 keyboard to RJ11, that might also be an option.
  • Must solve the chassis situation: it won’t do much longer to have the guts of the machine sprawling next to my desk. Would love to get a genuine Sun 2/120 deskside case, but I’m considering modding a fullsize PC tower case, if possible.
  • Make SMD cables: one 60-pin (A = control) and one 26-pin (B = data) with IDC connectors.

Old plan:

Before I managed to get a hold of a genuine Sun 2/120 CPU card I was planning on creating a clone based on the original schematics.

Components sourced so far:

CPU card

  • Motorola MC68010L10 (microprocessor)
  • 39.3216MHz crystal oscillator
  • Zilog Z8530A (serial ports)
  • AMD 9413 (timer)
  • National Semiconductor 58167 (real-time clock)
  • 2x 27128 EPROM (bootprom)
  • Xilinx XC2S200 FPGA (MMU, misc.registers and control logic)

I was planning to make my own CPU card and was drawing up a 1:1 copy of the schematic in Altium, including all the discrete logic chips, but would probably move the MMU and the control logic into the FPGA later, in order to save space/components/work. This plan now looks obsolete, though you never know.