Bob's Blog

doesn't seem to work, I just get a stuck sound with a black screen. I'm using Stella on OS X

Stella doesn't like how I bankswitch, sorry. It's a bug in Stella. Works on a CC and in z26. I plan to test in my new Krok Cart tonight.

Stella doesn't like how I bankswitch, sorry. It's a bug in Stella. Works on a CC and in z26. I plan to test in my new Krok Cart tonight.

I doubt that's really the issue, as I use a similar method in bB, and it works fine in Stella. The only real difference is all that indexed indirect stuff, which shouldn't matter.

 

EDIT: got it working in Stella. To do it, enter the debugger, type "reset" then exit. This suggests it isn't the bankswitching, but also suggests a startup/init problem with the demo or a bug in Stella.

IIRC, the bug has to do with how Stella handles the BRK opcode when the stack pointer is...$FF? Or something. So, technically, it doesn't have anything to do with how I'm bankswitching - the routine that bankswitches is called with a BRK opcode, which Stella doesn't like. If you start it in the debugger and step through the code you can see where it goes goofy; I can't remember exactly what happens, but it has to do with the stack pointer.

 

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Just got it working in Stella like you said. That's...weird.

IIRC, the bug has to do with how Stella handles the BRK opcode when the stack pointer is...$FF? Or something. So, technically, it doesn't have anything to do with how I'm bankswitching - the routine that bankswitches is called with a BRK opcode, which Stella doesn't like. If you start it in the debugger and step through the code you can see where it goes goofy; I can't remember exactly what happens, but it has to do with the stack pointer.

 

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Just got it working in Stella like you said. That's...weird.

 

I believe the problem is with the default bank. Stella starts 32K F4 and F4SC games in bank 7 not bank 0. I think the code assumes it starts in bank 0, however, I could be wrong. I modified Stella to start in bank 0 and the game begins as expected. Since it looks like that's the default for CC and Z26 I'll check those changes in to CVS so they'll be in the next release. Do 32K bankswitching carts always start in bank 0 or is it random?

IIRC, the bug has to do with how Stella handles the BRK opcode when the stack pointer is...$FF? Or something. So, technically, it doesn't have anything to do with how I'm bankswitching - the routine that bankswitches is called with a BRK opcode, which Stella doesn't like. If you start it in the debugger and step through the code you can see where it goes goofy; I can't remember exactly what happens, but it has to do with the stack pointer.

 

...

 

Just got it working in Stella like you said. That's...weird.

 

I believe the problem is with the default bank. Stella starts 32K F4 and F4SC games in bank 7 not bank 0. I think the code assumes it starts in bank 0, however, I could be wrong. I modified Stella to start in bank 0 and the game begins as expected. Since it looks like that's the default for CC and Z26 I'll check those changes in to CVS so they'll be in the next release. Do 32K bankswitching carts always start in bank 0 or is it random?

Hmmm. I believe actual 32K carts start in a random bank. Thanks for the heads up for this, I'll double-check the start up code in bank 7.