The real work of making a SBC with front pannel is literally the front pannel. There are a lot of switches, leds and drivers required. A software front pannel like the H8 is far less hardware. Also you don't need the old parts if you not building an ALTAIR/IMSAI at the schematically identical level. If you want functionally identical and still S100 then 74HCT or even 74LS parts of late origin are a better bet. From the block diagram level it makes little difference if a buffer is 1/6th of a 8t97 or 1/8th of a 74hct244. Same applies to the latches used. Using the octal vs hex parts will save a few chips. Also as a point I"d do the IMSAI as the altair design was bad on a good day. Too many oneshots and the FP connected to the bus via a bundle of wires (some over a foot long) making the bus noise worse. IMSAI was design with the front pannel plugging into a S100 slot directly and was cheaper, cleaner and more reliable as a result. Allison