$4014 switching

Celius · Post by **Celius** » Mon Jul 09, 2007 4:54 am

I was wondering a couple days ago if it was possible to switch RAM sections that are assigned to $4014 midframe. When I tried it, it worked, but not like I thought it would. I have one sprite being displayed in $200-$2FF, and midframe I check for a sprite #0 hit to have it switch to display $300-$3FF. The two sprites show up, but there is a constant flickering between the two of them. Is there a simple explanation as to why this happens? It doesn't make sense to me why it should.

loopy · Post by **loopy** » Mon Jul 09, 2007 6:04 am

Bregalad · Post by **Bregalad** » Mon Jul 09, 2007 6:21 am

Also, writing to $4014 is equivalent to writing 256 times to $2004. $2004 writes probably require rendering to be completely turned off just like $2007 writes.
Again, it's not really switching, you just change OAM data midframe. I have very few idea on where this could be usefull at all, exept if you're making a game with two split screen and absolutely want to bypass the normal 64 sprites limitation.

Celius · Post by **Celius** » Mon Jul 09, 2007 3:57 pm

I was trying to make a game hold more than 64 sprites, and I thought that might be useful. But maybe I shouldn't, I suppose. Oh well, thanks for the help anyways

.

tokumaru · Post by **tokumaru** » Mon Jul 09, 2007 4:32 pm

We've heard of games doing this before, but you have to stop rendering mid-frame for a while to do a second sprite DMA. Very few PPU operations can be performed while rendering is on and not cause glitches.