Hi Dave The N8VEM 6x0x host processor SBC can operate as either part of an ECB system where it is a peripheral co-processor or as a stand-alone system in control of its own ECB bus. The first mode assumes you have a Z80 or 80C188 based SBC controlling the ECB and the 6x0x appears as a peripheral co-processor with its own memory and IO. The ECB bus controlling CPU (Z80) can communicate with the 6x0x via an IO chip and the Z80 serves IO like floppy disk, hard disk, video, etc. coprocessor serving data as requested. The second mode is the 6x0x stand-alone mode where it has an expanded IO mezzanine board with a timer, ACIA, and dual PIO chip and a bus expansion connector. In addition, the 6x0x "stack" of boards can be further expanded to have its own ECB bus and directly control its own ECB peripherals like video, floppy disk, hard disk, etc. Either mode works just fine and it depends on the builder which way to go. In fact, you can build a system that uses both modes at the same time. However, it gets a bit too complicated in my opinion so I recommend choosing either one or the other. In short, the 6x0x host processor SBC works fine. It has CUBIX ported and that works as well as FLEX for the 6809. Both operating systems work just fine and are a lot of fun to experiment. There are plenty of PCBs left of all three of the 6x0x specific SBC boards The 6x0x host processor (supports 6809, 6802, and 6502 CPUs, ACIA, SRAM, ROM, ECB connection) http://n8vem-sbc.pbworks.com/w/browse/#view=ViewFolder&param=ECB%206x0x… st%20Processor The 6x0x IO mezzanine (timer, ACIA, dual PIO, ECB bus expansion) http://n8vem-sbc.pbworks.com/w/browse/#view=ViewFolder&param=ECB%206x0x… %20Mezzanine The 6x0x ECB backplane (connects to 6x0x IO mezzanine) http://n8vem-sbc.pbworks.com/w/browse/#view=ViewFolder&param=ECB%206x0x… B%20Backplane The project has been evolving over a couple of years and is fairly robust. There are several builders active with this system on the N8VEM mailing list. Thanks and have a nice day! Andrew Lynch