Thanks Neil, that was a neat design. In the end I have settled for the following “upgrade” of our SMB V2->V3. New additions:- Continuous bus clock (Phi) display using an Intersil ICM2718D IC frequency display chip and 3 common cathode displays at top of the board. Continuous display in a LED bar of one (any) port that the CPU may be outputting to (e.g. console out). Trap the S100 bus Error signal (pin 98), forcing the current CPU into a wait state, displaying the address etc. Cleaned up TMA0-3 switching circuit (GAL based circuit) for faster response (and any designated port). The 4 TMA LED’s now display the current bus status. Place a 6X2 0.1” set of jumpers at top of board to display the (buffered) main S100 bus lines with a multiport logic probe (USBee, Saleae etc.) Some tweaks on old circuits including a broad Vcc line to the external HEX display pins. The problem I’m currently having is the freerouter is having a problem finding a layout solution. Am trying a few more rearrangements of the furniture. John From: n8vem...@googlegroups.com [mailto:n8vem...@googlegroups.com] On Behalf Of nbreeden John, The N8VEM side of the house did a DSKY several years ago; I have one on one of my early N8VEM Z-80 builds; IMO it turned out really well. It used commonly stocked parts. If you decide to add an option for a DSKY type interface it might be a good starting point. -Neil -- |