SpritesMind.Net

> X is always 9-bits and Y is 9-bits in normal mode and 10-bits in double-resolution interlace mode.
> Yep, X is always 9-bit, Y is either 9-bit or 10-bit depending on whether interlacing is on or off.

I see, thank you! The SNES just doubles Y, so you can only move two pixels at a time in interlace ...

More fun here. The SEGA splash screen for Sonic is supposed to have a white background, yet I get black:

http://i.imgur.com/3JDspVx.png

Comparing to Mednafen trace logs to confirm I am writing the correct values at the correct locations.

What I see for pixel 0,0 on the screen is that there's no ...

Mike, what's up with this from BlastEm?

int16_t y = ((context->sat_cache[cache_address] & 0x3) << 8 | context->sat_cache[cache_address+1]) & 0x1FF;
int16_t x = ((context->vdpmem[address+ 6] & 0x3) << 8 | context->vdpmem[address + 7]) & 0x1FF;

You're building sprite coordinates from ((hi&3)<<8 ...

Whoo, brisk progress!

I have the best Sega Genesis game ever made already running! Just need input and audio output support to truly enjoy it :D

http://i.imgur.com/bZbo8Rl.png

The game is doing one weird thing, though.

001070 b22c cmp.b ($c00008),d1 00000001 000000df 00000000 0000ffff ...

Thank you everyone for the in-depth replies! :D

> Z80 you proabably cannot ignore for very long, there's plenty games that require Z80 to run to some extent.

Ah okay. I think in that case, I'll just start on a Master System emulator sooner to try and hash out a good Z80 core. I've emulated the ...

Hi all! I've recently begun work on a new Mega Drive emulator. Needless to say, I have lots of questions. I was hoping I could ask for some clarifications here. Given I have so many, my hope was to roll them up into one thread to avoid flooding the board. I hope that's okay! I know this is asking a ...

Chilly Willy wrote:Wow, MS compilers must really SUCK if you can't use inline assembly on them.

At least its had link-time code generation for the last six or so years. What decade do you think GCC will catch up? Would sure be nice not having to inline every critical function inside header files

And in the case of HDMA there will be no handshaking, so you'd better make sure you time it well, and you'd need to waste bandwidth sending some sort of flag, so you'd know the data has changed, probably.

HDMA data transfers use tight timing with no handshaking / flag checks. Technically, they ...

Whereas SNES is pretty much limited to it's 64KB RAM for samples, the Genesis is only limited by how much space you can spare on the cartridge.

This is not entirely true. While the SMP and DSP share only 64kb of RAM, the CPU and SMP can communicate with each other to transfer more sound data ...

I'm not sure I understand what you're saying. Amiga MOD instruments are based on 8khz samples and they sound great. And that's 8bit PCM vs the DSP 16bit output.

I would posit that 8-bit PCM sounds better than 16-bit PCM encoded as 4-bit ADPCM, but I haven't listened to the two side-by-side before ...

who's going to research things properly if it's all, apparently, documented?

Me and Nemesis ;)

Take the fact that there are now a lot of emulators based on Gens, instead of based on research, as an example of what I mean here.

That bothers me too. You almost have to be a historian to know ...

Probably not, its more likely that your context switches are not as optimal as they could be. Mine are down to two instructions, one of which I'd have to do anyway, and the other gets nicely pipelined and effectively takes less than a cycle.

Unless your cores only consist of one single monolithic ...

I forget the exact reason but it's documented somewhere ... the OS *is* expected to do this, so there may be a specific way of doing this that's much faster.

It breaks everything: branch prediction, pipelining, out-of-order execution, L1 cache, etc. Very bad stuff.

And I'd be really surprised if ...

The Mega Drive VDP has a H/V counter, but it has to be specifically read by the CPU.

Well, the same for reading the counter value from the SFC's PPU. It's just the H/V pin signals that the CPU polls every clock tick.

the only unsolicited output from the VDP to the Mega Drive is in the form of ...

you can't use a volatile variable as the basis for a lock, or shared data between threads where more than one thread modifies the value. The reason for this is the simple fact that as soon as you read the variable, it has already potentially been modified by another thread before you can write to ...