I'm a little confused, then. Are Nintendulator, Nestopia, FCEUX and the PowerPak getting this behaviour wrong?lidnariq wrote:That's partially an error in early VRC6 documentation. You have to write $24, not $04, to register $B003.
(The layout in the PPU viewer and the memory map in the debugger agree on vertical mirroring; I don't know why the "Mirroring Type" text disagrees)
Edit: the answer is yes. Correct emulation of this is not necessary for any of the Konami games, apparently, which never fail to set bit 5 of $B003.
This mentions replacing CHR A10 but says nothing about CIRAM A10. It also says "not replaced" for some values, which I'm confused how it's different from "vertical mirroring"... I guess if bit 4 of $B003 is set, normally CHR10-17 are replaced by the designated banking register, right? So this is an additional CHR override in that case? What gets overridden when bit 4 is not set? Is the incoming signal in that case PPU A10? Does the override also apply to CIRAM A10 instead of CHR A10?The wiki wrote:For the nametables, if the $20s bit of $B003 is set and the lower 4 bits of $B003 have one of the following values, CHR A10 is replaced