Fat was used in the Z80 basics from MS. Systems of not that had it were TANDY, NCR, NEC and a few others of the z80/cpm world. Side tidbit... 8086/88 part was available around 1978 (late) and systems using it were around in 1979. S100 and other systems were starting to build on it by late 1979 and DRI was late with CPM86. Hence the 8085/8088 boards for S100 and the other machine like rainbow that had z80/8088. There was at least on OS that ran on 8086/8 before DOS and that was a IRMX and I think ISIS-II as well. Allison