Note that no settings are stored in the Gate Array regarding register 3, but the PAL and Gate Array share an I/O port address.
Bit 14 Bit14 of the PAL selection address must be at 1 on CPCs equipped with CRTCs 0, 1, 2. It can be at 0 or 1 on CRTCs 3 and 4.
For compatibility reasons, it is strongly advised to always set bit 14 bit14 to 1 to select PAL.
See [https://www.cpcwiki.eu/forum/news-events/release-of-amstrad-cpc-crtc-compendium-and-amazing-demo-rev-2021/msg239536 Discussion on the forum]