Why RPI CM4 Adapter can't use mainboard WiFi?

I now have the RPI CM4 adapter too but am still waiting for CM4 to be in stock. I wondered about things like WiFi and EMMC but the store page says:

  • For all CM4 versions, without CM4 on-board WIFI module will NOT be able to use the WIFI function.
  • For all CM4 EMMC versions, will NOT be able to use the clockworkPi mainboard v3.14 SD card function.

But I am wondering why these are true?

For WiFi why can’t the CM4 use the mainboard WiFi chip like the CM3 does? The pins could be the same and driver should already be there for Raspbian kernel right?

This is a longer shot but re. EMMC others on forum say that other manufacture CM4 expander boards do support external SD. The post Can CM4 with emmc boot from SD card - Raspberry Pi Forums says that the EMMC occupies the normal (or new fast?) SD card signal lines, but https://forums.raspberrypi.com/viewtopic.php?t=302634 says there is an old “sdhost” on GPIO22-27 that can be used instead.

Maybe more generally, how does the RPI CM4 Adapter map the CM4 pins to the CM3 setup? (And for that matter, can I use the DevTerm adapter to put a CM4 in something else that expects a CM3 like a Turing Pi v1?)

Probably due to lack of available GPIO.

CM3 has 48 GPIO, CM4 has 28 GPIO. The WiFi/BT module on the 3.14 board uses 20 GPIO.

The adapter seems to be missing the parts for the 5V power supply. According to https://wiki.geekworm.com/CM4_to_CM3_Adapter If VBAT on the Carrier board is not 5V the adapter needs to provide it since the CM4 needs 5V.

VBAT on the 3.14 board is 5V so the 5V power supply on the adapter board is not needed.

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have you checked the pin-outs of the boards and checked if they match/are the same ammount?