Chuck said: Wow, that takes me back. I built one back in late 1984 on a board to fit into the expansion port of the C64. I believe it was Byte and I believe the project was originally for the Apple II. AFAIR The board had 16 buffers on the address lines feeding two precision resistor networks. One network for the lower 8 address lines connected to the oscilloscope X input. The other network for the upper 8 address lines fed the Y input. Giving you a 256 x 256 vector display of where the processor was accessing memory. I had a paying job to break software protection on some C64 games. And this help alot to determine which parts of memory where pieces of code were being stored. For a while I toyed with the idea of writing a vector verse of Tic-Tac-Toe by programatically putting jmp code pieces out in memory and jump from piece to piece in a loop create the graphics on the oscilloscope. --Doug Coward Poulsbo, WA The new home of the Analog Museum and History Center is http://www.cowardstereoview.com/analog