SpritesMind.Net

I can confirm this large ladder gap from measurements of DAC output levels: https://docs.google.com/document/d/e/2PACX-1vQ6CEUtCM3U6KKFD3i4lbMaF8muGQ5dez27OcpZOWRP2GgJviklr9rLIQut-LdoGfU4InazlIcbCvlG/pub (scroll down to YM2612 and zoom in on those 2 diagrams). Also, further discontinuities exist, es...

Cool

Regarding those remaining glitches, please check what I wrote here about re-fetching of sprite Y coord and size:
viewtopic.php?f=22&t=2604&start=15#p31287

Looks like it affects your emulator as well

Eke wrote:Strange. This is what I got, not sure where this comes from...

This looks like you still need to invert address bit 0 after converting the target address for 128k mode emulation.

No idea what causes the vertical stripes in the 3rd pic, though, incorrectly emulated illegal plane modes maybe?

I've been meaning to do some proper tests (though I'm sure someone else already has at some point), but it's good to have another data point. IIRC invalid horizontal size always gives you 32x1, invalid vertical size with valid horizontal size will behave as if vertical size was set to 32. On an unr...

Another possible issue: subsequent link field writes are done shortly before the sprite table address is changed. If this word is emulated to be written out too late then your emulated VDP might see it as not being written to the current sprite table as its address will have changed by then. As a re...

Yes, this code does indeed try to avoid FIFO stalls so the Z80 would not be halted when trying to prefetch. Actually, getting the timing right was not that difficult, I just adjusted NOPs until I got no more FIFO stalls (measured indirectly because FIFO stalls stabilise the timing on screen as measu...

1) no per column vscroll changes here, just per rasterline vscroll changes in the zoomer, no vscroll changes at all when it twists 3) yeah, this part requires halfway precise timing (but it's actually kinda relaxed since this routine also has to account for cycles stolen by the Z80) 4) we call them ...

I have another question regarding the debug mode when sprite plane is forced active (bits 8,7 = 0,1) : what happens for pixels where there hasn't been any sprite pixel (transparent or not) rendered in the line buffer ? The sprite buffer pixel color value is normally 0 in this case (same as a low-pr...

Awesome progress! Just wanted to point out the byte granularity DMA trick as explained in here , it might or might not give you a speed boost, depending on how your rendering works. All mega drives support it in one way or another, and some emulators already emulate it as well. MD1 and MD2 do as des...

Some questions about V28/V30 bit trick': - it makes HINT still occurring during vborders but also whole vblank i.e all 313 lines possibly ? yes. HINT runs continuously. Set register $F to 0 and you get a HIRQ on each of the 313 rasterlines. Set it to 156 and you get a HIRQ before raster line 156 th...

Lots of work was spent on getting rid of all the unwanted garbage, but 2 effect makes explicit use of what one would normally consider garbage ;) So based on a comment/question from alk on IRC, I'm guessing one of those is the dissolve of the white border in the post-Titancade screen. What's the ot...

- Sprites processing: ... ypos and size were read a second time during "phase 2" ... This could indeed be abused to produce tricky sprite behavior but more as a way to stress emulators than improving sprites capacity so I don't know if this was used in the demo ? --> yes, that behaviour is utilised....

This is our first item in a series of follow-ups about the making of Overdrive 2: everything we figured out about the Mega Drive hardware. I hope this will clear many things up and inspire more people to play with this platform! Just ask right here on the boards if there are any questions, or join u...

During "Overdrive" development we ran across a strange DMA related bug which later went away after a rewrite of that code section, but nonetheless I did some digging to find it, following an IRC chat. The code in question initiated CRAM DMA with pre-loaded registers as in "move.l d7, (a6)" (d7 = $C0...

Exodus seems to be about the only emulator that denies 68k -> z80 bus accesses while the z80 bus isn't fully acquired yet - pretty nice for debugging. But there's an implementation bug. In my case I'm just using z80 instructions with 4T maximum, so theoretically the 68k just needs a pause of 11 cycl...