Tyler Red wrote:Hey all, I've been silently following this thread but I want to chime in with what I'm seeing.
I have an original Famicom with the NESRGB v4 installed. I'm experiencing what I suspect is the color timing bug, but it's 100% repeatable; I'm playing the original Final Fantasy on an authentic NES cart via a 72 > 60 pin converter. When I exit any building in a town, most colors are lost. Here's a before and after:
![Image](https://i.imgur.com/zaodZad.png)
I have 100pf/220pf caps out for delivery today so I will try that fix!
This is the interrupt detection bug. It cannot be fixed by adding a capacitor to the CE# pin of the PPU, no need to try that. It's caused by changes I made to the interrupt detection logic that were not a very well thought out. It's a bit complicated it explain, but under the right conditions the NESRGB is blocking palette register writes because it thinks the PPU still rending when it isn't. I don't know how many games are affected by this one. I only know of one other and that's Bomberman 2.
You can probably fix Zelda by connecting a 10k resistor between the INT# pin (19) and +5V. That's a really hacky fix though, and it won't help Bomberman 2. I think the only proper solution to this one is an additional board that replaces the INT# detection logic in the FPGA.
Tyler Red wrote:I also have a question regarding the new jumpers: The current specification indicates J8 selects between CSYNC TTL (open) and 75-ohm (closed). However, the new version of the board does not have J8. While it does have J9, I suspect that enables/disables the LPF based on a post by Tim:
viletim wrote:The filter in the THS7374 is disabled by default but you can enable it by closing solder jumper J9 if you like.
Does anyone know what the CSYNC output is on the v4? And is it configurable?
It works the way it did on V1, that is the CS# pad is TTL sync with a resistor in series on the board. It will work when directly connected to TTL sync input (well... most of the time, but hardly anybody has a monitor that requires strict TTL sync), or directly connected to a 75 ohm video input, or connected to a 75 ohm video input with 330-470 ohm resistor in series inside the cable. No matter what you do it should just work.