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.
Bit14 of the PAL selection address must can be at 0 or 1 on CPCs equipped with CRTCs 0, 1, 2. It can must be at 0 or 1 on CRTCs 3 and 4.
For compatibility reasons, it is strongly advised to always set bit14 to 1 to select PAL.