sdm wrote:
To control the direction of screen scrolling (H/V).
The reason I'm asking is because there's no rule saying that you have to use a particular type of mirroring to achieve a particular type of scrolling... After all, there are games using 2 name tables that scroll in 8 directions just fine without ever changing the mirroring. You may need to use a few tricks to make 8-way scrolling 100% glitch-free, but it's possible.
I also mentioned 4-screen as an alternative to mirroring control. With 4 screens, you can have glitchless scrolling in any direction without tricks, and it's incredibly simple to add to a CHR-RAM cartridge: use a 16KB or 32KB CHR-RAM chip (which are way easier to find than 8KB anyway) and solder a wire to tell the NES not to use its internal RAM for name tables. It's a permanent setting, and the same chip will be used for pattern tables and name tables (4 of them).
Quote:
Somewhere is a diagram on how to connect WRAM to unrom? (If it requires adding something more than the wram itself.)
You do need a chip to handle the logic of when to enable the WRAM chip. The wiki has a page about this:
https://wiki.nesdev.com/w/index.php/PRG_RAM_circuitQuote:
Although I would rather use a mapper, which is commercial and generally available so that if necessary you do not have to combine too much to write the game on the card. (example: MMC1 when PRG up to 256, MMC3 when 512).
The MMC3 is a very nice mapper overall, but it may increase manufacturing costs unnecessarily if you you're not using some of its more advanced features, such as the fine CHR switching or scanline IRQs.