We have been doing some research on what is in the new macOS Sierra operating system, recently announced at the WWDC 2017. It includes a new file system, new hardware and software acceleration and something called Metal 2. But what does this mean for the older Apple Mac computers like the cheese-grater Mac Pro and the Mac Mini? 

It is certainly looking like macOS Sierra is going be a release with precious few user-visible improvements. That said, it would be unfair to call High Sierra a minor release as that would underplay the under-the-covers changes coming in High Sierra, some of which have been in the works for years now. New filesystems and graphics APIs are not exactly sexy and hard to demonstrate to most Apple users but let's see what there is and how it will impact using Pro Tools on the Mac platform.

Cheese-grater Mac Pro Support?

The good news is that we understand that both the 4.1 and 5.1 versions of the cheese-grater Mac Pro machines will support macOS Sierra. But it would appear that you won't be able to install High Sierra directly onto a cheese-grater without an update to the firmware which should be available from the App Store. However, if you can install High Sierra onto a drive on another more recent machine then transfer that drive to your Mac Pro, it will run High Sierra without the firmware update.

There is also some good news that there will be drivers for a new range of AMD graphics cards including;

• AMD Radeon 390X
• AMD Radeon RX 460
• AMD Radeon RX 470
• AMD Radeon RX 480
• AMD Radeon RX 580

But it isn't all good news, especially when it comes to video and graphics engine support as we will see later in this article.

New File System - APFS

The original Mac file system has its roots in HFS, which is around 30 years old. A lot has changed in 30 years in the computer world. Faster processing and bigger storage are just two areas that have changed exponentially and so Apple has decided it's time for a new file system.

In a nutshell, Apple explains that they are using a ‘new 64-bit architecture’, in which they have sped up response time and increased the security of encryption. When you install High Sierra for the first time, it will, by default, convert your boot drive to APFS irrespective of whether you have an SSD, a spinning hard drive or a Fusion Drive (although I hope you don't have a Fusion Drive as they don't play nicely with Pro Tools). The current Beta version does have the option not to do this, but it is unclear if this option will remain in the final release version of High Sierra. I suspect not if Apple's track record is anything to go by, as they will want users to adopt the new file system as soon as possible. However, there is continuing support for HFS+ in High Sierra. It will continue to boot from HFS+ partitions, and Disk Utility will retain the ability to format and work with HFS+ drives. 

What Benefits Will Come With APFS?

One of the more obvious benefits that Apple showed off in the WWDC keynote is the ability to copy files on the same disk without actually physically storing two different copies on the disk. It looks like native support for solid-state drives and encryption will improve but details are still a little sketchy at the moment but what Apple seems to be trying to get across is the increased flexibility the new file system brings both with current technologies and future technology, giving future proofing for the new file system. 

HFS+ can’t distinguish an SSD from a spinning hard drive, and so can't understand what a Fusion drive is either. Apple apparently relies on an under-the-hood technology called Core Storage that combines the drives and presents them to the OS and the filesystem as a single disk, and it’s Core Storage that’s responsible for shunting data to and from the SSD section of a Fusion Drive, depending on what apps and files you’re accessing.

But Core Storage is not aware of files, all Core Storage can see are blocks, and blocks on a hard drive look the same whether they contain essential system files, application, or a Pro Tools session. All the system can currently do with Fusion Drives is to keep track of how often blocks are accessed and move frequently used blocks to the SSD portion while maintaining infrequently used blocks on the spinning disk section.

APFS is much more intelligent. It can tell the difference between what is stored on hard drive blocks. It can also handle combining drives and move data around in the background. For example, if you’re frequently accessing something that takes up a lot of space but doesn’t benefit from extra storage speed like a video file, APFS can choose not to move that file to the SSD section, saving SSD space for other things and reducing the amount of wear on the drive. APFS can also keep file metadata on the SSD section while keeping files themselves on the spinning disk section, all of which will speed up things like Spotlight searches and trips to the “Get Info” window.

This may make Fusion Drives more Pro Tools friendly, but currently, it is too early to be certain one way or the other, so for now, our advice to avoid Fusion Drives on Pro Tools rigs stands.

Because of APFS supports snapshots, Time Machine no longer has to save multiple full copies of a file to your disk, it can just keep track of the specific changes. If you’re editing a Pro Tools session, say re-editing a clip, with the old HFS+ it meant saving two copies of the file, one that records your new changes and one just in case you want to go back. Now, with APFS it will just save the original file plus a record of the differences between the original file and any updated versions, which will also save on hard drive space too and mean writing less data to the drive, and that will mean the drive is likely to last longer.

We understand that APFS does more, this example demonstrates the key improvements APFS will bring.

New Hardware And Software Acceleration

macOS High Sierra will also have improvements in hardware and software acceleration with H.265 encoding for video and HEVC hardware acceleration, but only on newer Macs.

Neither is expected to take over from H.264 or JPEG, although apparently, that’s what they’ve each been designed to do; both can either maintain similar image quality at a lower file size or improve quality and/or resolution while keeping roughly the same file size.

HEVC roughly doubles the compression ratio of H.264, enabling it to deliver similar video quality at roughly half the file size (or higher quality and resolution at the same file size). With 4K content take up increasing streaming providers like Netflix and Amazon will be able to provide higher-resolution streams without quadrupling their costs, and new 4K-capable mobile devices will be able to shoot high-resolution video without eating up their storage so quickly. HEVC also supports 8K video, preparing the ground for even higher-resolution video in the future.

HEVC Hardware Acceleration Only On The Most Recent Macs

All High Sierra supported Macs will support HEVC, but only very recent models will support any hardware acceleration. This support is necessary because playing HEVC streams, especially at high resolutions and bitrates, is a  hardware-intensive operation as it consumes a lot of CPU processor cycles, This is likely to mean that smooth playback may be impossible on slower dual-core laptop processors. 

Apple says that somewhat bizarrely the HEVC uses your Mac’s processor rather than its GPU, apparently to save power especially in MacBook Pros with switchable graphics. This implementation limits HEVC hardware acceleration to Skylake or Kaby Lake processor Macs, even though some iMacs and MacBook Pros with older processors have GPUs that are capable of hardware-accelerated HEVC support. As we understand it, these are the Macs that will be able to handle hardware accelerated HEVC support in High Sierra:

• 27-inch 5K iMacs from 2015 and 2017
• 21.5-inch iMacs from 2017
• MacBook Pros from 2016 and 2017
• MacBooks from 2016 and 2017
• The iMac Pro, when it’s out

Note that this list doesn't include any Mac Pro, cheese-grater or trash-can, or Mac Minis, as these machines haven't had Skylake or Kaby Lake upgrades. But that isn't all, if you want support hardware acceleration for HEVC videos with 10-bit colour then it's down to Kaby Lake equipped Macs...

• 21.5-inch and 27-inch iMacs from 2017
• MacBook Pros from 2017
• MacBooks from 2017

Metal 2

Apple has announced Metal 2 with new optimisations and APIs and up to 10x better draw call throughput. There is also to be a Metal Developer Kit with a ThunderBolt 3 enclosure with an AMD Radeon RX 580 graphics card and a USB-C hub, and Apple is also introducing Metal for VR in macOS High Sierra.

It would appear that Apple sees Metal as the way forward for graphics and GPU computing on its platforms. Apple’s OpenGL support in macOS and iOS hasn’t changed at all in years.

Metal 2 is apparently primarily a technology for developers, so a lot of its improvements will only be of interest to developers, but there are some improvements for end users, too. People with newer GPUs should expect to benefit from some performance improvements, not just in games but in macOS itself; Apple says the entire WindowServer is now using Metal, which should improve the fluidity and consistency of transitions and animations within macOS. This implementation can apparently be a problem on Macs when driving multiple monitors like we use on Pro Tools rigs and remember that although we don't play games on Pro Tools systems, the demands that plug-ins and metering place on a computer mean we, more and more, need gaming like features.

Apple is also making Metal 2 the go-to API for supporting VR on macOS. With Apple's newer iMacs and its native support for external Thunderbolt 3 GPU enclosures as with Metal 2, developers will also be able to distinguish between external and internal GPUs. Thunderbolt 3 is slower than an internal PCI Express interface and may need to be treated differently and because apps will need to be able to fall over gracefully if an external GPU is removed.

Apple says that every device that supports Metal should support at least some of Metal 2’s new features, but the implication there is that some older GPUs won’t be able to do everything the newer ones can do. The Metal support list includes these Macs:

• MacBook (2015 and later)
• MacBook Air (2012 and later)
• MacBook Pro (2012 and later)
• Mac mini (2012 and later)
• iMac (2012 and later)
• Mac Pro (Late 2013)

So no cheese-grater support although the Mac Pro Trash-can is on the list, but it is still early days, and there is no publicly available  hardware list that shows which devices will see the full benefits of Metal 2, but that will come with time.

The Differences Won't Be Easy To Spot But The Cheese-grater Mac Pro May Be Dead

If you have got this far, this is still a broad overview of the most relevant changes. The differences between using a Mac running Sierra and one running High Sierra won’t be easy to spot, but they are there, and it is clear that High Sierra is mainly about future proofing. But it is also evident that the macOS is moving on and is leaving behind a lot of the older hardware, especially the cheese-grater Mac Pro, which could have an impact on how long we can continue to run our beloved tower based Mac Pro machines with the latest Mac OS.