Two-way cache in yabause

[mic]

I was using 0.9.7 when testing this, so you can ignore my comment if the problem has already been fixed..

What I was trying to do was this:

Set up a two-way cache by writing 0x19 to the cache control register (0xFFFFFE92).

Copy some code/data to the explicitly cached region at 0xC0000000-0xC00007FF.

Run some code from that region.

When I ran my program in yabause it didn't work. I looked in the debugger and saw that the main SH2 was stuck on the stack somewhere (PC had some weird value like 0x06000952). But I thought my code was correct so I decided to try it out on my Saturn. Sure enough; it works just fine.

So it seems like yabause has a problem with executing explicitly cached code.

JSYK.. 😉

 

[mic]

Here's a small test that demonstrates this problem: http://jiggawatt.org/satcache.zip

Upload the binary to 0x06004000. The result should be a green screen (and it is on a real Saturn). In yabause I get a red screen which indicates that the code in cache wasn't executed properly.

 

[Guillaume]

I've just spent some time this evening to get it working.

The problem is Yabause only allow execution of code in some specific areas of the memory and that wasn't one of them 🙂

Anyways, I commited a fix for it. You can download the latest SVN and compile with

"./configure --enable-exec-from-cache && make"

to test it. The fix is not enabled by default, as I'm still not sure of the best way to handle it.

 

[Chilly Willy]

Do you only support 2K+2K mode? You can actually use all 4K of the cache when the cache is off. I don't know that anyone actually does that, but it would be best if you supported it.

 

[Runik]

Do you only support 2K+2K mode? You can actually use all 4K of the cache when the cache is off. I don't know that anyone actually does that, but it would be best if you supported it.

I had to add the 4K of RAM in Saturnin to have the sprites in 3 Dirty Dwarves displayed, and after testing the game on Yabause, it has the feature too 😉

 

[Chilly Willy]

I had to add the 4K of RAM in Saturnin to have the sprites in 3 Dirty Dwarves displayed, and after testing the game on Yabause, it has the feature too 😉

So someone DOES use that mode... cool. Thanks for the info. 🙂