SBC6120 Project - a Historical 21st Century PDP-8 Implementation
The SBC6120 system was originally designed by Bob Armstrong who also wrote the necessary software and drivers for it. As designed and assembled the single board computer kit allows to install and run OS/8 or OS/78 as well as any other program running under these operating systems. It provides an IDE connector for a hard disk or a memory card and a serial interface. An internal stackeable bus connector is also there. The print format 6¼" x 4¼" (168 x 117mm) is close but does not match the 160 x 100mm standard EU card and thus does not fit in such a EU card rack - my original idea housing the board and peripherals.
Internal view of my SBC6120 box built in 2005, on the underside is the 5¼" disk.
To experiment with the basic system and its software I proceeded to install the board in an existing case remaining from a previous unfinished project and added a recovered power supply (+12 and +5VDC), an old PC 5¼" HD (not much capacity needed, but LBA capable) and a new VT6 terminal kit to the system. More pictures of this 2005 implementation are shown here and it has served me well running OS/8 and writing various batch files and small PAL8 helper programs. My later versions used a simple +5VDC only supply and either 2½" laptop HD or better an IDE adapter and SD card as shown in my FP6120 implementation.
Unfortunately all kits are sold out, but the information is still worth looking at. I built several of the computer boards, they all worked well and Bob's BTS6120 monitor program is well done. An interesting addition mentioned above is Bob's VT6 terminal kit, that provides an interface to the serial port for a VGA video terminal and an IBM keyboard (US keys). I've even used one on a real PDP-8/E to avoid using a PC and a terminal emulator. This too is unfortunately sold out.
Notes on Making the SBC6120 Work and Play
Setting up a few ready to run OS/8 2½" HD for the surplus SBC6120s for sale, a writeup was produced that covered the steps needed to get an SBC6120 board up and running. While not all resources may be available to the reader, it shows the important steps and gives a few tips to get off the ground.
The document with pictures of the set-up and procedure can be found here and there is also a detailed guide to the use of the PDP-8 chess program CHEKMO-II. This program is actually much more than a toy - using a chessboard to visualize the moves - you may find it quite challenging to win against it. Recently at my VCFE/CH show display, an obviously experienced chess player went through a full game and - lost.
