I've updated my Arduino code so that I can stream the ROM code to it and load it into my flash cartridge. This will hopefully make coding go faster now that I can use the python assembler and not have to write machine code by hand. I'm still using the ROM v3 code, but I can update to v4 soon.
I notices in the ROM code it takes quite some time to get through the boot sequence with verifying the memory. Since I'm still using the Arduino to drive a slower clock to the board, I had to change that to pump up my clock speed. So after hacking the internal timers to fast PWM mode, I can now get from 7kHz up to 8MHz. Unfortunately I can't get the exact 6.125MHz I need for video, so at some point I'll have to put the clock chip back in.
I've found I have 3 LEDs come up in sequence which means the memory checks are succeeding. The 4th LED does come on, but it blinks at a very high rate. I had to slow the clock down to see it. At about 125kHz it's noticable. It does not do the LED scroll sequence, so it is still having some problem somewhere in the code.
I also noticed I have to manually issue a reset to the board after it powers up usually to get the code running. I'm not sure why, but I'll have to look into that. It's possible my bank switching is powering up at 1 which would start running code in the wrong bank. I suppose I could add a piece of code at the beginning of the top bank so that if it ever boots there it will bump it over to the correct bank and continue booting. But I feel like it's REAL close to running.