As mentioned elsewhere I need to control myself when browsing eBay. I saw these two circuit boards online and could see they were Motorolla 68000 CPU boards, likely industrial in nature. Sold as XBUS computers that were massive. Got them for a ridiculously low price of £20 and could see that one of them has socketed CPU and other support chips. I want to build a 68k SBC to sit alongside my Z80 one, so buying a CPU would be the bulk of that cost, assuming it worked. There were other chips that might be useful but you never know, perhaps it could be bought back to life.
The listing had this:
| 2 x XBUS Vintage Computer Motherboards Might be useful for the RAM, Processors, EPROMs, TTL, etc. Quite a few of the ICs are in sockets, particularly on the older board. Believed to have been serviceable when removed but they have been stored for a while. |
A search online revealed no information for the following search terms:
XBUS 68000
HAM 90/48 (Written on main board)
HAM96/17 (Written on a RAM module)
68000 industrial computer
Nada! Zip… Nothing… I asked the eBay seller but not much else.
Well lets see if we can breath coms life into it. Firstly power…
There is a large connector on the board and tracing the pins to the ICs, which will be running at 5v, gives a clue as to the voltages here:
There is likely to be a 12v level in there somewhere, perhaps even some negative voltages, but 5v should be enough to breath some life into it.
Using a trusty (and a little rusty) old AT power supply hooking up the connections with jumper leads is straight forward:
Applying power to it there IS life there:
The LED shows something and there are clock signals now appearing on the CPU! A nice little 68010
Now, with no known IO it is tricky to test. Lets take a deeper look.
IO Ports
There is a 25-pin D connector on the edge of the board.
Loads of XBUS expansion ports
What looks like a power header
A 34 pin dual-in-line connector (Floppy?)
Search for life
The most logic step is to connect to the serial port. There is a serial UART controller IC near the port and a crystal. The IC is a NS16450N, the clock is rated at 2.4576
The odd rate of 2.4576 MHz is a classic for 9600 Baud serial connections.
Lets hook things up and see:
Plug in my Amber Terminal and set the defaults:
On boot the terminal shows some activity, pushing characters onto the screen.
Will try and capture this again and show. There is some life on there.
Large IC audit:
DP8473 Floppy Disk Controller PLUS-2
MC68A40P
DP8473 Floppy Disk Controller PLUS-2T
NS16450 – Universal Async Receiver/Transmitter