Yeah, it had breakpoints only for addresses. So I'd have to refer to the listing to find some addresses (which is a PITA), but mostly I'd do breakpoints on a couple JMPs that were always in a fixed location in RAM, so it worked OK for that. And pressing 1 would enable/disable CPU tracing, and 2 for SPC tracing (no breakpoints for that, though). You could watch them run simulatously, it was kinda cool watching a transfer happen from both sides, heh.