It’s all Apple’s fault. I was perfectly happy with my 2011
27-inch Core i7 iMac and its SATA SSD upgrade when I heard that
the company had finally started supporting third-party NVMe as
of macOS High Sierra. My iMac (old as it is) replaced a Windows
PC with an NVMe SSD, and though the iMac is a far superior
experience overall, I missed the speed of the NVMe SSD running
the operating system. Boot Camp, Logic Pro X…great stuff, but
if I could just add NVMe and run macOS from it.
In case you aren’t aware, NVMe is fast—two to six times the sustained
throughput of SATA (depending on the drive), with, at times,
one-tenth the seek latency. If you’ve used a
MacBook Pro from the last couple of years, you’ll
understand: Apps pop open, files load and save in and instant,
and boot times are ridiculous.
The thing for me is, covering storage for PCWorld has its
perks. Just lying around were an Akitio Thunder3 PCIe
enclosure, as well as several PCIe NVMe drives left over from
reviews. All I needed was a Thunderbolt 3 to Thunderbolt 1/2
adapter for NVMe rapture, right? Hah! After updating to High
Sierra, Murphy’s law caught up with me big time.
Don’t do what I did
The first issue was the adapter. Seemed to me that any old
Thunderbolt 1/2 to Thunderbolt 3 adapter should work. This is
what they’re for, right? Apparently not. As it turns out, only
one of the several on the market will do the job, and
that’s Apple’s $50 adapter shown below.
The $50 units from Akitio and Startech I tried initially were
uni-directional in the wrong direction—they would only handle
Thunderbolt 1 or 2 devices attached to a Thunderbolt 3 port.
This experiment was the exact opposite, a Thunderbolt 3 device
to a Thunderbolt 1 port. The bi-directional Apple adapter does
both. It’s what you want.
After the Apple adapter was in place, the next issue was
Thunderbolt PCIe enclosure compatibility. The early-to-market
models I tried initially—the aforementioned Aktio Thunder3 PCIe
and Akitio Node—work fine on Windows PCs, but they
use TI’s 65982 communications chip, which predates Apple’s
adoption of Thunderbolt 3. Any enclosure using this chip with
throw the message you see below. Murphy was laughing.
Finally, Akitio sent a Node Lite which uses TI’s newer 65983 (as does
Akitio’s Node Pro) chip that Apple does support, and I was sure
that NVMe bliss was nearly upon me. Wrong again. Shut up
I should point out that I could’ve avoided all this with the
Akitio Thunder2 PCIe, which I later acquired
for testing. It’s completely compatible with Thunderbolt and
Thunderbolt 2 Macs. The issue here is that many Thunderbolt 2
boxes are reaching end of life. Also, Thunderbolt is the future
and performs much better on newer Macs. And there’s only a
minor performance penalty with the adapter.
NVMe: Modern implementations required
In my testing for PCWorld’s Akitio Thunder3 PCIe
review with a 1.2TB Intel 750 NVMe PCIe SSD inside,
the combo read at about 2 GBps and wrote at well over 1 GBps.
Nice, but I certainly wasn’t expecting the same results on
a Thunderbolt 1 port, with an adapter, and older 2nd generation
Intel CPU in play. Neither was I expecting the 350 MBps reading
and writing that the Node Lite/Intel 750 combo initially delivered on
my iMac. Slower than SATA? Seriously Murphy?
After some head-scratching and other physical manifestations of
frustration I won’t discuss, it occurred to me that the Intel
750, being an older enterprise product from the days of NVMe
1.1 (the NVMe spec is now up to 1.3) might need a firmware
upgrade. It did. There was one.
Performance jumped to a much more respectable 566 MBps reading,
and 644 MBps writing. That’s better than the 529 MBps and 499
MBps my iMac’s internal Samsung 860 Pro delivers, but hardly
the 800 MBps to 900 MBps I was hoping for. Seek times were
halved, but again, not the 10-times reduction that I’d hoped
As it turned out, the 750 is a bit of an outlier. Both the
Intel Optane 900P and the Samsung 970 EVO I tried next bumped
those numbers up a good 100 MBps. I tried the drives on a
slightly newer iMac Core i7-3770, and there was a gain of about
50 MBps. While the price versus result ratio of this upgrade is
debatable—the improvement is noticeable, but not
earth-shaking—on my iMac, you’ll see at better throughput/value
with faster CPUs and chipsets
I also did a quick test on a friend’s 2015 MacBook Air with 20
Gbps Thunderbolt 2, and things really got moving with a healthy
1.2 GBps read/write rate. Thunderbolt 3 proved the panacea,
with read/write rates that roughly equal what I’ve seen from
the same drives mounted internally on Windows PCs.
To flesh out the performance picture I used the two
aforementioned enclosures: Akitio’s Thunder2 PCIe (a native
Thunderbolt 2 product), and the Thunderbolt 3-based Akitio Node
Lite. I tested the three drives I mentioned above in each
enclosure: Intel’s 750 PCIe, Intel’s Optane 900P, and Samsung’s
far more affordable 970 EVO.
I tested under macOS on the aforementioned Core i7-2600 iMac, a
2016 MacBook Pro Core i7-6700, and a 2015 MacBook Air i7-5650KK
using Blackmagic’s DiskSpeed with the drives formatted to HFS+.
I tested using AS SSD and CrystalDiskMark under Windows 10 from
the same dual-booting Core i7-2600 iMac, as well as PCWorld’s
Core i7-5820K storage testbed. I reformatted the drives to NTFS
for the Windows 10 tests.
The MacBook Pro and storage testbed are native Thunderbolt 3
and required the Apple adapter when testing the Akitio Thunder2
PCIe. The MacBook Air was Thunderbolt 2, and iMac is native
Thunderbolt 1 and required the Apple adapter when using the
Node Lite. Below are summarized some of the most pertinent
Aside from a few earlier product that are probably already
end-of-life, all the other NVMe SSDs I lightly tested delivered
a nice boost. Most were M.2 types mounted on a $25 Adata PCIe
adapter. Slower NVMe drives will do almost as well as the
faster ones under Thunderbolt 1, but their weaker performance
will definitely show up with 40 Gbps Thunderbolt 3 and to a
lesser extent, 20 Gbps Thunderbolt 2. Take a look at PCWorld’s
SSD coverage for relative performance numbers.
If you’re interested in the specific results—and there were
significant differences between the various combos—you can find
them in the spreadsheet capture seen below. The spreadsheet
also shows the seek results from AS SSD. Note that these were
noticeable slower on the iMac than our Windows test bed, for
reasons yet to be determined.
A couple of notes. As I said earlier, the Apple adapter
impacted performance only slightly, and the difference was not
apparent to the naked eye. You may also notice that combos
tested faster under Windows in terms of throughput. There was
also a noticeable difference in seek times between the iMac and
our Windows test bed. Whether this is the difference in the
hardware, drivers, or the fault of my test methodologies, I was
unable to determine at the time of this writing.
Also, the Boot Camp utility crashed sometimes when I tried to
create a Windows partition when macOS was run from an external
NVMe drive. The solution to that is also under investigation,
but Boot Camp won’t let you create the Windows partition on an
external drive at this point anyway.
In the graphic above, there’s improvement using NVMe over
Thunderbolt in most cases, but it might not be enough to
justify the expense. Note however, the models listed are top of
the line Macs with fast SSDs. If your internal storage is less
capable, that’s a different story.
Other vendors that produce Thunderbolt PCIe enclosures are
Sonnet, Highpoint, and Startech. Some are for external graphics
cards and Macworld hasn’t tested them. Ask the appropriate
questions before buying.
Upgrading your Mac’s hard drive to an SSD of any type is a
transformative performance experience. NVMe over
Thunderbolt is faster than an internal SATA SSD, and an easier
upgrade, but that 30 to 40 percent bonus and halved seek times
will cost you $400. A DIY internal SATA SSD upgrade is around
$125. Your choice.
If you already have a fast SSD in your system, then the upgrade
to Thunderbolt NVMe isn’t going to rock your world. Everything
depends on the vintage and type of storage in your Mac. If
you’re not getting the types of numbers you see above, it’s a
pretty sweet upgrade. The upgrade to my own iMac wasn’t “gotta
have it” though now that it’s up and running, it’s hard to go
back. Just sayin’.