Does this XBios thing use legal opcodes? Will it run on our MANY upgrades?
Lance will lose lots of sales...
The XBIOS source code is freely available. You can look for yourself for illegal (undocumented) opcodes. I never found them very useful and always assemble programs without them. Using illegal opcodes would generate error messages while trying to build the binary in MADS Assembler.
ah. I forgot the 3x 65816 boards... (hides and runs...)
I tested some games with 65816 CPU in the emulator, they seem to play the same. One thing I do notice is when calling DLI at bottom of the display list to erase the player/missile graphics, the process is done much faster and where sprites get cut off right at the last display list line. The process is geared toward a 6502c running at 1.79 mhz.
Right now I am looking at doing this disk access directly through the OS or with the XBIOS. I am experimenting with both processes. It is something extra I am looking into and if I can get it to work great. If not, I won't use it. I think I am having problems because the game is designed with most of the IRQs and being shut off except for reading keyboard/break key. Have to look to see what hardware registers need to be set to allow disk access.
I think I found the issue with XBIOS. The source does not have that little routine loaded at $03C0, that sets a few parameters and calls SIOV in the OS. Very important. You have to keep in mind when cartridge is booted. Nothing is loaded from the OS and all RAM is available for the software on the cartridge to do whatever it needs to do with it. Can totally use all of page 0, stack, and from $0200 to $FFFF except the chip IO and area mapped for the cartridge ROM itself.
Edited by peteym5, Sun Jul 15, 2018 10:42 PM.