I had been meaning to pick up a 9010a for awhile, and finally did so recently. I do firmware development for a living, and have spent my entire career doing low-level processor and hardware debug .. so I was never satisfied with the indirect or brute force approach to fixing games. There is really no substitute for getting right into the system to debug, as long as you have the skills to figure out how the system is supposed to work (figuring out the address map, accessing memory-mapped devices, bank switch configs, schematic reading, etc).
As expected, I've flown through my debug queue pretty quickly - e.g. on the first trial run, the Fluke RAM test found a stuck address bit that had been causing watchdog resets on my Defender for awhile during the rug test.
The MAME driver source is pretty helpful for getting address map details at a glance (usually commented at the top of the file). I also like to use the MAME debugger to see how the system works - e.g. setting watchpoints on ROM/RAM ranges to see how it's being used, watchpoints on I/O port accesses, and even occasionally stepping through the code to see how it works.
It would be even more ideal to have full ICE-style debug capabilities for these games, but as it is the 9010a and MAME debugger work pretty well.
LeChuck
