mirror of https://github.com/bsnes-emu/bsnes.git
ffd150735b
byuu says: Added VDP sprite rendering. Can't get any games far enough in to see if it actually works. So in other words, it doesn't work at all and is 100% completely broken. Also added 68K exceptions and interrupts. So far only the VDP interrupt is present. It definitely seems to be firing in commercial games, so that's promising. But the implementation is almost certainly completely wrong. There is fuck all of nothing for documentation on how interrupts actually work. I had to find out the interrupt vector numbers from reading the comments from the Sonic the Hedgehog disassembly. I have literally no fucking clue what I0-I2 (3-bit integer priority value in the status register) is supposed to do. I know that Vblank=6, Hblank=4, Ext(gamepad)=2. I know that at reset, SR.I=7. I don't know if I'm supposed to block interrupts when I is >, >=, <, <= to the interrupt level. I don't know what level CPU exceptions are supposed to be. Also implemented VDP regular DMA. No idea if it works correctly since none of the commercial games run far enough to use it. So again, it's horribly broken for usre. Also improved VDP fill mode. But I don't understand how it takes byte-lengths when the bus is 16-bit. The transfer times indicate it's actually transferring at the same speed as the 68K->VDP copy, strongly suggesting it's actually doing 16-bit transfers at a time. In which case, what happens when you set an odd transfer length? Also, both DMA modes can now target VRAM, VSRAM, CRAM. Supposedly there's all kinds of weird shit going on when you target VSRAM, CRAM with VDP fill/copy modes, but whatever. Get to that later. Also implemented a very lazy preliminary wait mechanism to to stall out a processor while another processor exerts control over the bus. This one's going to be a major work in progress. For one, it totally breaks the model I use to do save states with libco. For another, I don't know if a 68K->VDP DMA instantly locks the CPU, or if it the CPU could actually keep running if it was executing out of RAM when it started the DMA transfer from ROM (eg it's a bus busy stall, not a hard chip stall.) That'll greatly change how I handle the waiting. Also, the OSS driver now supports Audio::Latency. Sound should be even lower latency now. On FreeBSD when set to 0ms, it's absolutely incredible. Cannot detect latency whatsoever. The Mario jump sound seems to happen at the very instant I hear my cherry blue keyswitch activate. |
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