If anything they are both generic S100 crates. Most S100 systems needed at least two serial ports. One for the console and often if there was a modem one for that. In my case I used a DEC 100 printer which happens to be a serial interface rather than parallel. Those that did run multiuser often had many more than two ports. I have a few S100 4 port cards and have seen systems easily capable of running 8 or more users. If anything S100 was the PC of the era in the sense that there wer plenty of crate (bus and power) vendors and a plethora of board suppliers. At times mixing and matching was like PCs post XT era in that most boards nearly worked but there were variantion on interpretation on bus standard. The Apple and SS50 bus machines (6800 and 6809) were also common too in the way of machines with some kind of bus that multiple things could be plugged into. In Europe there was ECB bus and I suspect others. So in most cases S100 implies generic system but little beyond that. For example for S100 the cpu list included everything up to and including 386s! By specifiying a vendor of S100 system we are usually talking about box/CPU/FDC as an agragate system from vendor. It was common to have memory from the same of multiple vendors and possibly added IO. A pure single vendor S100 system is sometimes uncommon. It just so happens that NS* marketed the Horizon as complete systems that were business ready and modestly priced as a complete hardware and software package. Allison