Note that no settings are stored in the Gate Array itself regarding the MMR register. But the PAL and Gate Array share an I/O port address so that it appears to be the same chip to the programmer.
Bit14 of the PAL selection address can be at 0 or 1 on CPCs equipped with CRTCs 3, /4. It must be at 1 on CRTCs 0, /1 and /2 (The result is not guaranteed).
For compatibility reasons, it is strongly advised to always set bit14 to 1 to select PAL.