PSP Extra RAM?

poorkingz · Post by **poorkingz** » Sun Apr 19, 2009 7:41 am

I'm trying to see if I can use the PSP's extra RAM in user mode for assembly code. I know that the normal the range of the user memory is 0x08800000-0x0A000000, but I don't know where the extra ram area starts or if I could even jump to it. Anyone know?

J.F. · Post by **J.F.** » Sun Apr 19, 2009 12:12 pm

It's at 0x0A000000 to 0x0BFFFFFF. You can use it directly as long as you don't use PSP_LARGE_MEMORY = 1 in the makefile. Just set a pointer to it and fetch/store like normal. I did that in Doom for the PSP for the TV framebuffers (this was before it was known how to extend the vram to its full 4MB for framebuffers in vram for TV out).

poorkingz · Post by **poorkingz** » Sun Apr 19, 2009 12:50 pm

Alright. Everytime I try to access it (using assembly) I freeze. Probably since I am trying to use it with a UMD game, not my own homebrew (I do have UMD Cache on ofcourse). But thanks for the info anyway :).

J.F. · Post by **J.F.** » Sun Apr 19, 2009 3:48 pm

I see, yes, if it's not your program running, the OS may still be using the extra memory for something else. In that case, you have to use the system functions for allocating memory, like sbrk does to set up the heap. I suggest you look at that code. If you look at one of the early threads on the Slim memory partitions, you'll see which partition the extra memory is, at which point you may be able to allocate from it. I say MAY because I don't know if anyone has tried such a thing.