replying to "Lo-tech_Z80_CPU_Test_Adapter It's an excuse for making and selling a PC board. A 40 pin DIP CLIP does that and more: for probing with a scope or logic analyzer. Most system boards don't have the space or clearance for daughterboards. A stand alone Z80 CPU tester is just a clock source, 5V and pull-up resistors, feeding the Z80 NO-OPS. Then watch the CPU go thru its paces -- jeffj