The item up for auction is a working GMX Micro-20 68020 Single Board Computer with SASI connected Xebec controller for the 200Meg harddrive and a 5.25" 720K Floppy Drive . This includes the original power supplies (separate 5vdc and 12vdc units) and UNIFLEX operating system with assembler and Absoft Fortran 77 compiler. This computer can be operated using the Windows XP hyperterminal via serial port and and the system can be structured in a multi-user mode with up to 4 terminals. Screen shots of its startup are shown. Documentation is thorough for the Debug, Uniflex System, Screen Editor and the hardware in five (5) notebook volumes. The Fortran 77 compiler is without documentation although the Absoft Pro Fortran manual is available here. Hardware circuit diagrams, timing and protocol is described in detail with Motorola manuals for the 68020 processor and 68881 coprocessor . While the original independent 5v and 12v power supplies are provided it can be powered up using a 4 pin molex connector from a desktop computer (normally harddrive power). This is the 16MHz version of the board and the computer was assembled with all new components except for the Xebec S1420 controller which was surplus from Xebec in Carson City. This controller supports the hard drive and daisy chained floppy drives. Another port allows an Atari 520ST computer to be the terminal (which earlier was my primary means of operating it). The SASI (Shugart Associates Standard Interface) is a subset of the SCSI interface. Most current SCSI devices are compatible with SASI as added features of SCSI are seldom used. This was assembled in 1986 with a million bytes of memory and was superior to most mainframes of that time. It has seen use for trajectory analysis, ionospheric modelling, GPS reductions, radar vernier analysis and surveying closure verifications among other things and is in working order. A double density full height floppy is included as an added drive for greater interface flexibility and it includes the necessary terminating resistors. The cover was originally borrowed from a Heathkit Amp/Preamp but was reclaimed when that unit was found to be a collectible. Sales literature and original invoice are included. |