SpritesMind.Net

Unfortunately it doesn't speed anything up, the access time during V-Blank is the same as when the screen is turned off. However you can get more time to do DMA transfers by "letterboxing" the display, where you turn off V-Blank early (say line 200) and then back on late (say line 8 of the next fram...

I've seen an issue on some flashcarts and my own dev hardware where there are graphical glitches in this game, during the 7 Force battle when you fight the cat robot thing. It's happened with several different Genesis consoles. Here's how it should look: https://youtu.be/AaSsBtFD4Xc?t=182 Now what I...

Wow, great job! Nice to have a very technical post to start the new year. :) About the sprite Y read parts, any idea why it goes up to 15 and not 7 given that there's eight possible sprites per scanline? Or is this a side effect of having to read data in some wider width? (say 16 bits at at time, so...

Mask of Destiny, good catch! I've edited my post for clarity. unlicensed EA games (Budokan, etc.) use H40 mode with the wrong combination of RS1,RS0 set, How does that even work, that should result in an invalid TV signal. For one of the combinations of bits yep, it's a scrambled mess, for the other...

Bart did a good write-up on some poorly documented/undocumented aspects of the 68000 too: https://emu-docs.org/CPU%2068k/68knotes.txt Other quirks include: MOVEM reading one address past the source location: http://gendev.spritesmind.net/forum/viewtopic.php?f=13&t=2010&p=25882 CLR to memory being re...

When doing DMA from the 68K address space to VRAM, what happens when the Z80 tries to read banked RAM memory during a long transfer? I'd assume the Z80 is halted until DMA is over, but I think this would affect sample playback. Is there a priority system where the Z80 can always complete an access f...

The Game Genie disables all the user-accessible registers when it is running a game. The only thing you could do is checksum the ROM and verify if it is bad or not, which would indicate the Genie was patching one or more locations. I can't remember if the Genie software fully clears out RAM and VRAM...

I'd try gently pressing on around the edges of each of the surface mount chips to see if anything changes. That would indicate a bad solder joint where a pin isn't contacting the pad on the PCB well. Or press gently on the PCB to flex it a bit and see if there's any changes. I know the cables and Ge...

If the Z80 is held in the reset state (by $A12000) then busreq will never be asserted and the loop will never exit. This is because the Z80 reset logic has a higher priority than the bus request logic. Maybe check for any unintended writes to $A12000 in the sound/joypad routines and verify the Z80 i...

Wow, very nice! Also impressed to hear music and some SFX too.
Given the limitations of the Genesis, the title screen came out well.

I opened a few carts today. I can confirm that at least Phantasy Star IV and Sonic 3 do not implement the write protect bit in either game. I wonder which other games would be candidates to look at? Off topic: My Super Street Fighter II cartridge had a modification compared to db-elec's, there's a 0...

Happy birthday! Thanks for all your contributions to this forum.

It's in the 32X documentation that's floating around. Also I noticed Beyond Oasis (and perhaps others?) write to these Sega-defined mapper registers despite not actually having one (I checked a real cart), presumably as the development hardware had it. Since the functionality isn't present in the ca...

- how is it possible to generate DTACK ? I understood it means address is available on the address bus but who defined it (when it's ready) ? You assert DTACK when you detect the address range you want is being accessed, meaning /AS is low and the address lines match the address range you want. For...

Sometimes you see communication methods where there is no handshaking (acknowledgement or status indicators) and I don't know how they are supposed to work reliably. :) I realized since the circuit has a 74HCT74 there's a 2nd flip-flop we can use, so I expanded the schematic a little. Now when you w...