Strength and duration.
Earth spins about its axis at approximately 1'200 km/h and has a circumference of approximately 40'000 km. So if a severe coronal mass ejection were able to continue bombarding Earth for 33.33 hours on end, then it would definitely affect the whole planet.
I wouldn't count on that if I were you. Consumer-grade devices are virtually unshielded against anything at all. Hell, both my phones and their batteries already start acting up when there's a sufficient degree of ionization of the surrounding air by atmospheric conditions. Among other things, the batteries will short out and start leaking their stored energy into the ionized air.
Also, there's a reason why enterprise-grade computer hardware uses ECC registered memory modules. And even that is not entirely fail-safe. But consumer-grade computers either way don't have that — ECC registered memory is very expensive, and the motherboard and CPU must also support it — let alone that it would have been implemented in handheld devices. This is why cosmic radiation and/or atmospheric conditions can render any modern computing device unstable.
Whereas EMPs are concerned, the most reliable electronics are those with vacuum tube technology and point-to-point wiring. In fact, some Russian military aircraft are still using this technology, exactly because of its resilience against an EMP. Of course, vacuum tubes have their own issues on account of reliability. They periodically require replacement, they're expensive, they are usually suspended in a heavy steel chassis, and they are of course not exactly what you could call shockproof.