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NES - some optimizations to ReadMemory(), ~1fps speed up

This commit is contained in:
adelikat 2012-08-19 20:38:20 +00:00
parent 70929679d5
commit 6473321100
1 changed files with 30 additions and 9 deletions
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39
BizHawk.Emulation/Consoles/Nintendo/NES/Core.cs
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@ -238,18 +238,39 @@ namespace BizHawk.Emulation.Consoles.Nintendo
public byte DummyReadMemory(ushort addr) { return 0; }
public byte ReadMemory(ushort addr)
{
byte ret;
if (addr < 0x0800) ret = ram[addr];
else if(addr >= 0x8000) ret = board.ReadPRG(addr - 0x8000); //easy optimization, since rom reads are so common, move this up (reordering the rest of these elseifs is not easy)
else if (addr < 0x1000) ret = ram[addr - 0x0800];
else if (addr < 0x1800) ret = ram[addr - 0x1000];
else if (addr < 0x2000) ret = ram[addr - 0x1800];
else if (addr < 0x4000) ret = ppu.ReadReg(addr & 7);
else if (addr < 0x4020) ret = ReadReg(addr); //we're not rebasing the register just to keep register names canonical
else if (addr < 0x6000) ret = board.ReadEXP(addr - 0x4000);
else ret = board.ReadWRAM(addr - 0x6000);
if (addr >= 0x8000)
{
ret = board.ReadPRG(addr - 0x8000); //easy optimization, since rom reads are so common, move this up (reordering the rest of these elseifs is not easy)
}
else if (addr < 0x0800)
{
ret = ram[addr];
}
else if (addr < 0x1000)
{
ret = ram[addr & 0x7FF];
}
else if (addr < 0x4000)
{
ret = ppu.ReadReg(addr & 7);
}
else if (addr < 0x4020)
{
ret = ReadReg(addr); //we're not rebasing the register just to keep register names canonical
}
else if (addr < 0x6000)
{
ret = board.ReadEXP(addr - 0x4000);
}
else
{
ret = board.ReadWRAM(addr - 0x6000);
}
//handle breakpoints and stuff.
//the idea is that each core can implement its own watch class on an address which will track all the different kinds of monitors and breakpoints and etc.