Fine SCX timing is confusingly described

[Ptival]

In the "Rendering" section, it is written:

At the very beginning of Mode 3, rendering is paused for SCX % 8 dots while the same number of pixels are discarded from the leftmost tile.

In the "Pixel FIFO" section, it is written:

As stated before the pixel FIFO only operates during mode 3 (pixel transfer). At the beginning of mode 3 both the background and OAM FIFOs are cleared.

I found this very confusing as the two statements seem contradictory with each other (can't drop pixels from empty FIFOs).

The answer seems to be that the thing described as happening "at the very beginning of Mode 3" in fact happens quite later:

• Mode 3 starts and the FIFOs are cleared,
• Now the pixel fetcher is going to put stuff in the BGW FIFO,
• Now the pixel fetcher is going to be pre-empted by the OBJ FIFO until there are pixels in the OBJ FIFO,
• And finally, the SCX % 8 dots that drop pixels from FIFOs happen.

So I'd suggest replacing "At the very beginning of Mode 3" with "Towards the beginning of Mode 3, once both FIFOs have been populated with the first pixels", or something along these lines.

[ISSOtm]

To be fair, the entire “Pixel FIFO” article needs to be overhauled. Hence #379... but that's currently stalled by a lack of maintainership. (If you feel able to help there... that would be very helpful!)