The new MacBook Pro has USB-C ports for everything – power, I/O, and graphics. And although USB-C ought to support HDMI monitors just fine, I’ve found that it doesn’t work all that well with my 15″ MacBook Pro. I recommend sticking with DisplayPort until Apple resolves the issues.
First, a bit of background: The “Thunderbolt 3” USB-C ports on the Late-2016 MacBook Pro computers support native “alternate mode” HDMI and DisplayPort video, in addition to USB 3.1 and Thunderbolt (PCIe) connections. I picked out a set of cables and adapters for my 15″ MacBook Pro with Touch Bar and found that, although DisplayPort works flawlessly, HDMI was pretty flaky. And my experience matches that of many others.
TL;DR: Stick to DisplayPort, which works great, and do not buy a USB-C HDMI adapter (even Apple’s own Digital AV Multiport Adapter) unless you know it works. And don’t count on 87W USB-C pass-through charging working with any adapter.
The Bad News: HDMI is Flaky At Best
HDMI is everywhere, since most inexpensive monitors are just repurposed TV’s. HDMI is also the new common denominator for those of us who travel and use projectors. So I’m very disappointed to report that HDMI cannot be trusted to work with the new Late-2016 MacBook Pro.
I purchased the Monoprice Select Series USB-C HDMI Multiport Adapter and found that it did not work with any monitor I have encountered. Some, like my Dell P2715Q, were not detected at all. Others, like the Dell S2715H at work, were detected by macOS but did not display an image. The monitor “knew” there was something happening but it remained black. On the other hand, this adapter did work with the Dell U2415 monitor.
There are numerous reports online about flaky behavior with Alternate Mode USB-C HDMI adapters, ranging from complete failure (as in my case) to connect to wakeup/power-down issues to plain old flakiness. Even Apple’s own USB-C Digital AV Multiport Adapter doesn’t work reliably – it’s got just 2 stars on the Apple site, with many issues reported.
I believe this is a software issue and hope Apple will address it in future revisions of macOS Sierra. Since my 1080p external monitor was detected, it seems that the hardware might be functional. Perhaps 4K monitors won’t work, but 2K or less HDMI should be OK once Apple issues software updates. But how can Apple justify selling a non-functional first-party adapter for something as critical as HDMI?
Furthermore, although Apple’s support site indicates that the 87 Watt USB-C power adapter will charge the 15″ MacBook Pro through their Digital AV Multiport Adapter, this appears to be untrue. I can confirm that my Monoprice adapter will not pass enough power to charge the battery: Although the “gong” sounds and the lightning bolt appears, the computer is not charging. And people are reporting the same behavior from the Apple adapter.
The Good News: DisplayPort Works
I purchased a couple of USB-C to DisplayPort adapters from Monoprice and am pleased to report that they both work just fine. As hoped, these simple adapters natively and passively attach Alternate Mode DisplayPort from the MacBook Pro’s integrated AMD GPU through the Intel Thunderbolt controller and connect perfectly with the monitors I’ve tried.
I’ve been using my best-choice Monoprice USB-C to DisplayPort cable with my Dell P2715Q 4K monitor for a few days and it was really flawless: No visual artifacts, full resolution and refresh rate, and no issues with sleep or wake-up. As a test, I bumped the internal display to native 2880×1800 resolution and the Dell monitor to 3820×2160 resolution at 60 Hz and everything worked perfectly.
The Mac automatically switches from the Intel HD Graphics 530 built into the Skylake CPU to the AMD Radeon Pro 450 as soon as it detects the external monitor, which was almost instantaneous. It was amusing to watch the connectivity change over in System Report as I unplugged the cable.
Note that others have reported sporadic issues with DisplayPort as well. But these issues seem to be rarer than with HDMI. So I still recommend DisplayPort.
The Late-2016 MacBook Pro is an all-new hardware platform for Apple, so I’m not surprised that some initial issues are apparent with third-party hardware. But it is disappointing that even first-party Apple adapters don’t work. There’s no excuse for this kind of flakiness for mainstream uses like HDMI connectivity!