Apple silicon Macs are now attracting those who haven’t changed their Mac for quite a few years. In recent weeks, I’ve had questions from quite a few who are making the huge leap from a ‘cheesegrater’ Mac Pro, early iMac 27-inch Retina display, or MacBook Pro 2012, often running macOS Mojave, to an M-series Mac. This article looks at some of the big differences you need to consider when upgrading.

32-bit to 64-bit

If you’re coming to Ventura or Sonoma from Mojave or anything earlier, you have to replace all 32-bit software with 64-bit. Currently, there’s no way to run 32-bit apps or QuickTime codecs normally on Apple silicon, although some have had success using UTM, or running WINE using Rosetta 2, but those are slow and can’t be relied upon.

Before trying to move any apps from your old Mac, bring them as up-to-date as you can, if possible ensuring that they’re fully 64-bit. Once they’ve been copied across, any 32-bit apps simply won’t run, so trying to update them on Apple silicon would require you to download and install a 64-bit version before you can even start. Some of the worst problems come in software components rather than whole apps. This article looks at the difficulties you may encounter.

A few apps never survived the transition to 64-bit. For those, you may need to retain your old Mac so you still have access to them. That should only be an interim solution: Macs and macOS will never provide backward compatibility in the future, so now’s the time to identify a modern replacement and start migrating to it.

HFS+ to APFS

Although APFS was introduced in High Sierra, HFS+ remained widely used, most significantly for Time Machine backups. Although recent versions of macOS have retained the ability to continue backing up to HFS+ volumes, they’re effectively deprecated and come with some serious disadvantages. The best plan for Time Machine backups is to archive those you have been making on your old Mac, and start fresh backups to an APFS volume for your new Mac. Because macOS still supports HFS+, old backups and volumes in that format remain fully accessible to your new Mac.

While APFS is designed for and works best on SSDs, many use it on hard disks. Over time, severe fragmentation can slow disk access badly, but that’s less of a problem when the contents of the disk are largely static, as in most media libraries, and many still back up to APFS volumes on hard disks without running into significant problems. Ultimately, though, your backups will be best on an SSD when you can make that move.

Intel to Arm

The most obvious difference with your new Mac is that it uses Arm processor cores rather than Intel ones, and the code they run is different. By now, almost all supported software should be available in Universal format, thus capable of running native on Apple silicon Macs. For the few that aren’t, provided they’re fully 64-bit they can be translated to Arm code by Rosetta 2, a free and automatic download from Apple. The first time you try to run Intel-only code on your Apple silicon Mac, it will invite you to download Rosetta to enable that.

Rosetta generally works excellently, and because it translates code into Arm instructions, it usually runs apps at near normal speeds. It also works around another problem you could encounter with older software, which may be unsigned. One of the requirements for all Arm-native executable code is that it’s signed, even if only with an ad-hoc signature. Rosetta automatically signs the code that it translates when running Intel apps, so saving you the bother.

There are some limits to what Rosetta can translate, though. It can’t work with kernel extensions or whole operating systems such as macOS. Kernel extensions are bad news in Apple silicon Macs anyway, as to enable their loading you have to run your Mac at reduced security and explicitly allow them, a setting in Startup Security Utility in Recovery. Avoid installing any kernel extensions on your Apple silicon Mac: recent versions of most apps that used to require them should now use more modern alternatives such as System Extensions, which are run with Full Security enabled.

Single system volume to SSV

Another change you’ll soon notice when coming from Mojave or earlier is that the single startup volume has been replaced by a boot volume group, within which the Signed System Volume (SSV) contains most of macOS. This extends the architectural change introduced by Catalina, and has substantial effects on how macOS works. The new layout for M-series Macs is shown below.

The two volumes you’re most concerned with are the System, which is now a read-only snapshot of the System volume, and its paired Data volume, containing some writeable files for macOS, common folders like /Library, and Home folders. Also paired with those is the Recovery volume, explained below.

Because the SSV is read-only and sealed with a tree of hashes to detect any changes, it can only be modified by macOS installers and updaters, and is verified down to the last byte and bit to guarantee that it’s exactly as Apple intends. This forms part of the Secure Boot process that makes modern Macs so secure.

Apple silicon Macs have extremely fast internal SSDs that are intended to be used as your Mac’s startup disk. Although they can be booted from external system disks, they work best from their internal storage. Because the SSV is checked each time your Mac starts up, there’s no point in reinstalling macOS as a generic solution to problems. I have several articles here that explain the wider implications and impact of the SSV in more detail.

System Settings

As soon as your new Mac has been personalised and configured, you’ll notice a big change: gone are System Preferences, replaced by System Settings. These will take a bit of getting used to, and still have some rough edges, but they do have the advantage that you can enlarge their window vertically. This makes it easier to work with long lists of items, such as in Privacy & Security.

When you’re looking for a specific setting, try the search box at the upper left. For example, searching for time zone should enable you find that setting immediately. The View menu also contains a helpful list of different settings.

Some, such as Network Locations, remain hard to locate, though. That’s hidden in a popup menu from a button bearing the ellipsis … at the foot of Network settings.

Recovery

Should you need to use Recovery Mode on any Apple silicon Mac, there’s no point in using traditional startup key combinations. The only way to start up your new Mac in Recovery is to press and hold its Power button. Although there is a way of doing this from a restart, if you need to enter Recovery Mode you normally do it when starting it up, if necessary shutting it down first.

Keep holding the Power button until you see that it’s loading Options, then release it. You’ll be shown its initial screen, from where you can set it to restart in Safe mode, enter hardware Diagnostics, restart it from a different boot disk, or enter the main Recovery menu for other services including Disk Utility. I have a fully illustrated guide available here.

While you can change startup disk in System Settings, this is the only way to enter Safe Mode, or to access Startup Security Utility.

Migration and iCloud

When you’re moving from one Mac to another running the same version of macOS, it’s usually simplest to migrate, either during setting up or later using Migration Assistant. The greater the distance between the two versions of macOS, the less reliable this becomes, and by the time you’re looking at going from Mojave or earlier to Ventura or Sonoma, it’s probably going to cause more problems than it might solve. That said, I know of some users who have migrated similar distances and were pleased with the end result.

My personal preference is not to accept the invitation to migrate when first setting up a new Mac. Instead, I configure the primary admin account, usually with the same short user name for compatibility with the older Mac. I then install all macOS and other system updates and ensure that everything’s working fine, particularly in networking.

Only then do I connect the new and old Macs back-to-back, using a Thunderbolt 4 cable if both have ports, to ensure the best transfer speed between them, then open Migration Assistant on the old Mac, and on the new one. This allows you to migrate carefully, without any rush, and to select items like applications carefully, so you won’t regret overwriting new settings with old, unless you want to.

This is now greatly aided by shared data in iCloud. Even if you don’t ordinarily share your Mac’s keychain in iCloud, or synchronise calendars or address books, consider doing so prior to setting your new Mac up. So long as you allow sufficient time for the old Mac to sync fully, when you start your new Mac up it can then benefit from those passwords and other data without your having to mess around with keychains and data files. Once synced, if you really don’t want to continue sharing via iCloud, you can then turn that off.

Finally, if you’re a regular user of iTunes, you’ll know that Catalina replaced it with separate media apps, and that iPhoto has been supplanted by the Photos app. Although moving your media libraries shouldn’t prove a problem, there are many who have got into deep difficulties doing so. I’ll here defer discussing them for another time, and just wish you the best of luck.

You may also find my compilation of articles covering Apple silicon Macs useful, as they go into greater detail about these and other aspects.