What risks can be when using SDK 5.2.0 + S110 6.0.0 on older nRF51822 QFAACA/C0 chips?

Question

Hi,
it happened that we have some hardware boards populated with older chips rev. QFAACA and some with newer rev. QFAAG0 but we need to share same software. As I read newer chips should use SDK 5.2.0 and older 4.4.2. But SDK functions are not compatible and firmware cannot be simply compiled with both SDKs. What risks can happed when 5.2.0 SDK wil be used with QFAACA chip? Was it just not tested or there is known serious problem?

Ole Morten · Accepted Answer

The reason for this recommendation is that versions later than 5.2.1 hasn't been fully tested on second revision chips, so there could be issues that we don't know about due to the slight hardware differences. This issue is an example of such, and there could potentially also be others. 
 However, both S110 version 6.0.0 and SDK 5.2.0 contains nice changes, that I'd strongly recommend you to build upon. Also, for production you'll almost certainly actually end up getting second revision chips by now. For development, I'd therefore recommend you to just use the most recent versions of the S110 and SDK with your current chip, but just make sure to get second revision chips for final testing and production.