NON–VOLATILE RAM (along with
PRAM, parameter RAM) stores
things like your startup disk
selection, screen resolution, time
zone, and sound volume. The
system management controller
(SMC) deals with battery and heat
management, what happens when
you press the power button or open
or close a MacBook, the ambient
light sensor (auto–brightness),
keyboard backlighting, and (on the
few iMacs that support it) external
video input.
Resetting NVRAM or the SMC
shouldn’t be necessary, but it’s
worth trying when nothing elseĽ{hv#|rxu#sureohp1#Wr#uhvhw#
NVRAM and PRAM, restart or turn
on your Mac and immediately hold
Opt+Cmd+P+R (you might want
d#iulhqg#wr#khos,#xqwlo#lw#Ľqlvkhv#
booting into macOS. It may restart
itself again during the process (see
bit.ly/apple-nvrampram).
Resetting the SMC is slightly
trickier, and the method depends
on which Mac model you have —
vshflĽfdoo|/#krz#lwġv#srzhuhg#dqg#
whether it has the T2 security chip.
See bitly.apple-resetsmc for details
of how to do this. Don’t worry, you
won’t need a screwdriver, but
qlpeoh#Ľqjhuv#zloo#fhuwdlqo|#khos1COULD RESETTING THE NVRAM OR
SMC HELP TO SOLVE MY PROBLEM?CAN I CHECK WHICH DRIVE MY
MAC IS STARTING UP FROM?WHAT DOES A FLASHING QUESTION
MARK ON STARTUP MEAN?HOW DO I USE RECOVERY
TO GET MY MAC WORKING
PROPERLY AGAIN?Your Mac can’t find a drive to boot macOS X
from. The first thing to do is wait, because
occasionally a minor problem causes this to
happen as a one–off. If the Mac eventually starts
up, go to System Preferences > Startup Disk and
select your startup drive. If not, try Recovery
(see “How do I use Recovery to get my Mac
working again?”, below right).MORE SERIOUS PROBLEMS
A variety of interventions may rescue a stuck Mac
Recovery is a stripped–down macOS
that’s kept hidden for emergencies. To
enter Recovery, restart or power up
your Mac and immediately hold down
Cmd+R until you see the Apple logo.
If Recovery fails, you’ll see a globe
instead, meaning your Mac is trying
to recover by downloading tools (you
can force this by holding Opt+Cmd+R
while starting up).
Either way, you get four options:
Restore From Time Machine Backup (if
you have one); Reinstall macOS; Get
Help Online (browse Apple Support);
and Disk Utility (see page 20).
Reinstalling macOS may fix things
without deleting your data. Restoring
from Time Machine is more drastic,
but just as easy — it may take a
number of hours, but should get
Your startup drive is chosen in System you back to normal.
Preferences > Startup Disk. In most
cases you’ll only have one bootable
drive. If you hold Opt while starting up,
Startup Manager offers an explicit
choice of drives, plus “EFI Boot”, which
lets you start up temporarily from your
Time Machine backup.Image rights from: Apple.
Feature
22 MAR 2020 maclife.com