CHR_TRN is normally buffered to SNES WRAM, and only gets transferred during a PCT_TRN. However, the transfer point is when the border finishes fading (so the transfer is seamless), so it's actually possible to send PCT_TRN, then CHR_TRN during the fade, and have it work.

Alfred Chicken apparently relies on this.

• Investigate timing window
• Document all this

Note that this also means the border tiles do NOT update immediately upon CHR_TRN!