Thunderbolt 3, USB 3.1, USB Type-C: Making Sense of Connections


Things change so quickly in the tech space that even professionals sometimes find themselves stymied by the incessant and confusing terminology surrounding certain protocols (like the ones we're going to discuss today - Thunderbolt and USB). I remember the days of 8-track tapes, but I also remember when tapes were surpassed by CDs, and CDs were surpassed by MP3s, and now how MP3s are being taken over by streaming music sources. Thinking back on those days, I was constantly barraged by new terms every day that made it difficult to slog through the buzzwords: single- and double-layer CDs, WAVs, AAC, OGG, and MP3s. I longed for the days when I recorded music to a cassette from my boombox (from AM radio stations, no less) and had to manually rewind it with a pencil stuck through the tape spool.

The same goes for Wi-Fi protocols. Yes, I remember baud modems and BBS groups and ICQ messaging. Now you kids come along with your newfangled LOLs and DDoS attacks and dual-band, tri-band rock band routers and 802.11 ac—what happened to good old-fashioned 802.11 a, b, g, and n? All relegated back to the alphabet, it seems, to be replaced by new combo terms like 802.11 ac and ax. Punk kids with your fancy Internet and your loud music.

The same thing is happening to connections. If you were using and fixing computers back in the Pentium processor days, then you may remember the pain of trying to hook up peripherals to your computer. Your mouse and keyboard needed a dedicated PS/2 connector or serial port (oddly enough, many motherboards still have this as an option). Your printer? Probably a gigantic parallel port connector that was about the size of a small flash drive these days. External hard drives? How about an old SCSI connector? And how about adding a ZIP drive with a colossal 100MB of space—that’s the equivalent of 85 floppy disks! I think you can find them on eBay, and they come with a free set of dentures.

USB took care of all of that by adding a “one ring to rule them all” mentality, with an interface (Universal Serial Bus) that was supposed to uniformly combine the speed and ease of a single interface into one connector. Unfortunately, no one told Apple, which continued to offer less popular connectors such as Firewire 400/800. USB 1 debuted in 1995 with an amazing 12 Mb/s of speed. Always concerned about backward compatibility, the USB 1.1 protocol came along, which allowed the speed to decrease to 1.5 Mb/s for slower devices. By the time USB 2.0 showed up in 2000, the speed had jumped to a whopping 480 Mb/s, and ports were backward compatible with older USB 1.1 devices—which meant your USB 1.1 device could work in a USB 2.0 port, but a USB 2.0 device would not work in a USB 1.1 port. In the same year, USB flash drives became a thing, and users were able to transfer data easily between a computer and flash drives at an appreciable rate and at a higher capacity than before.

It’s never enough. Along comes USB 3.0 (also referred to as USB 3.1 Gen 1) with superior transfer speeds of 5 Gb/s (you read that right). It’s backward compatible with USB 2.0 devices, but it will only transfer at the host computer port speed; in other words, if you use a USB 3.0 port with a USB 2.0 device, the transfer speed will only top out at 480 Mb/s. As if this weren’t as confusing as pre-calculus, we now have USB 3.1 (also referred to as USB 3.1 Gen 2), with an amazing transfer rate of 10 Gb/s, and the ability to transfer at that rate over a standard USB 3.0 cable. So if you have a USB 3.1 host port, and a USB 3.1 device, but are using a USB 3.0 cable, you’ll still see speeds of 10 Gb/s. So that’s it in a nutshell, right? Wrong. Use the chart below to get your head around USB speeds, and then we’ll talk about USB Type-C and Thunderbolt™.

Not your type?

Okay? Now we have USB Type-C. USB Type-C isn’t about the speed, it’s about the design. Before all of this, USB connectors came in different sizes: Type A, Type B, mini A, mini B, micro AB, and micro B. Sometimes, finding the right cable for your device was even more confusing than figuring out your USB speed. You also had to determine which was the correct orientation for your cable—some connected in specific configurations, and flipping a cable around in the dark or behind a cord-crowded PC was a pain. USB Type-C goes in either way, upside down or right-side up, taking the guesswork out of the plug-and-play game.

The USB Type-C connector can potentially provide up to 100 watts of power, so you can use it to power and charge cell phones, laptops, and tablets, as well. Whether or not your port or device can be powered is determined by the logo. The Power Delivery (or PD) ports are signified by a battery symbol around the logo (see below).

USB 3.0, USB 3.0 with Power Delivery, USB 3.1, and USB 3.1 with Power Delivery

Another new feature of the USB Type-C connector is its ability to send DisplayPort signals over the same cable and connector as USB signals; once a defining advantage of Thunderbolt over USB. This allows users to hook up external displays over the same simple port as their mice—nice! Unfortunately, not all computers with USB Type-C ports have to support DisplayPort over USB Type-C, so be sure to check your computer’s specs since compatibility is not guaranteed.

Bring the Thunder!

So now that we’re finished with USB types and connectors, let’s move on to Thunderbolt. Thunderbolt is a transfer technology (developed by Intel®) that provides PCI Express data and DisplayPort functionality in one cable. The chart below shows the advancements made in Thunderbolt speeds and how it compares to other protocols.

Thunderbolt also allows you to daisy-chain more than one peripheral to your existing connection. Because of the host-to-user design of USB technology, as opposed to the peer-to-peer design of Thunderbolt (and FireWire before it), USB could never connect more than one peripheral in a “chain” to your host computer —imagine using one computer, connecting an external USB hard drive to it, then trying to connect another USB hard drive to that one, and so on. USB can’t do that (unless you use a hub), but Thunderbolt can, with up to six devices. USB is also not bi-directional, which means that you can't transmit and receive data at the same time, while Thunderbolt can. Also, because Thunderbolt uses a PCIe bus, you can even add external graphics cards to Thunderbolt-equipped computers, something you can’t do over a USB bus. New USB Type-C connectors will also be directional, but that function will only be available with Thunderbolt host ports. While the original Thunderbolt and Thunderbolt 2 ports used mini-DisplayPort connectors, Thunderbolt 3 uses the USB Type-C connector for all needs. The “one cord to rule them all” is finally here.

Will Thunderbolt 3 take over all transfer protocols in technology’s near future? It certainly is appealing, with its 40 Gb/s speed and USB Type-C connectivity. It also appeals to creative professionals in audio and video recording, with its ability to transfer large files quickly for near lossless experiences. But until we see Thunderbolt 3 added as a feature to more laptops and desktops, it remains on everyone’s wish list. Hopefully, this primer on USB 3.1 vs Thunderbolt 3, with a side selection of connector types, will help you make the right decision when purchasing new equipment this season.

Have any questions, comments or concerns? I know I couldn’t include everything in this short primer, but if you have anything to add, do so in the Comments section, and we’ll get back to you as soon as we can!


Thank you for the clear easy to understand article. I am a true tech amateur. I am trying to transfer home movies from old mini dv tapes to my Mac desktop that has a thunderbolt 3 port. The camcorder has DV and USB2.0 ports. I am assuming the usb2.0 port would be better, but I’m not 100%. If I used the usb2.0 access I believe I would need a usb female to thunderbolt 3 female adapter, which I’m having trouble finding. Your expertise and advice would be greatly appreciated. Thank you! 

My apologies. I meant to write that I think I would need a thunderbolt 3 male to usb female adapter. 

Hi Lisa!  You would just need a USB-C to USB-A adapter like the one in the link below.

I'm looking at jumping from a Windows PC to a new MacBook Air and have these questions:

Will all my older USB 1 and USB 2 flash drives work with the MacBook Air USB-C ports?

Can the MacBook AIr Thunderbolt 3 video port be adapted to drive a monitor with DVI input?

Will the MacBook be able to read .jpeg, .docx, and .xlsx documents?

Thank you.

You can use your flash drives if you have the USB-C to USB-A adapter.  (

Here is a USB-C to DVI adapter for your monitor.  (

Your Mac will be able to read Jpeg files just fine.  You would need to use the Pages and Numbers apps to read .docx and .xlsx files.  

Hi, thanks so much for sharing the article and wish you had a great holiday. I know that Thunderbolt 3 has max speed of 40gb/s. When I look at LaCie website, both Thunderbolt 3 (w/ USB-C) and USB-C portable hard drive have a max speed of 130mb/s. My questions are: why is it much slower than 40gb/s; why is Thunderbolt 3 more expensive than USB-C while they have the same max speed. Thanks!

Thunderbolt is the technology and USB-C is just the port.  The max theoretical speed of Thunderbolt 3 is 40gb/s but this just means this is the max bandwidth.  Devices like external hard drives have bottlenecks.  In this case, it's the hard drive itself.  I don't think there is any drive out there that would even come close to letting you transfer 40gb/s.

Hi, I have a MacBook Pro 2018 with 4 Thunderbolt 3.0 ports. I tried to buy a LaCie Rugged USB-C, but instead came a LaCie Rugged Thunderbolt 2+USB-C .
Now I am wondering whether it was in fact a good thing (and then I could buy a MiniDisplayPort-To-USBC adapter, or whether I should return it.
The question is: with the appropriate adapter, will I have more speed buy using the Thunderbolt 2.0 cable (directly attached to the hard drive), or will I get the same speed using the removable USB-C cable provided with it, just because my Mac has Thunderbolt 3 ports?
The other question is: if I get the LaCie USBC-only version, will I be limiter to USBC transfer speed, or will I get Thunderbolt 3 speed?

Thanks for your help.

USB-C would just be the connector type.  It wouldn't make any difference if you connected the LaCie drive to your Mac with an adapter or direct connection.  You speed will be limited by the bottleneck and in this case would be the LaCie drive since it can only support Thunderbolt 2.   If you purchase a LaCie with Thunderbolt 3, your theoretical speeds would be greater than a drive with Thunderbolt 2.


I have a laptop with one Thunderbolt 3 port. I'm planning to buy 2.5" USB3.1 Gen2 enclosures, come with type C to type cable. So, does Thunderbolt 3 compatible with USB3.1 Gen2? Thanks.

I also asked the manufacturers are those enclosures compatible with thunderbolt 3 port, but no answer.

" type C to type C"

The drive should work just fine with your Thunderbolt 3 USB-C port.  Most TB3 ports support USB-C peripherals as well.  Actually, I don't recall seeing a computer with TB3 USB-C not supporting USB drives but I'm sure there are one or two out there.

I recently bough the 16TB G|RAID from G-Tech with Thunderbolt 3.  I've got it plugged in to my brand new 13in MBP but it doesn't seem to charge like it says it will.  If I plug in tradition wall power it charges and as soon as I unplug it the laptop goes into battery mode.  

Any Suggestions? 

The G-Tech G-RAID drive you have does not have the ability to power and charge your MacBook Pro.  

Very useful article, but I'm afraid it has my old grey matter spinning! I have an iMac with two thunderbolt-1 sockets, a firewire socket and a set of usb-2 sockets. I have my lacie external drive usb-c plugged into one of the usb-2 sockets. Would it increase the speed if I used the drive's usb-c lead and an appropriate adaptor into either the firewire/thunderbolt sockets?

For optimal performance, I'd like to suggest the Apple Thunderbolt 3 (usb-c) to Thunderbolt 2 adapter.  You can plug the USB-C side to the drive and connect your Mac to the adapter using a Thunderbolt male to male cable.

Thanks for the response Geoffrey. However, I have come across this statement on the Apple communities website:

"The Thunderbolt adapter is Thunderbolt only, even though Thunderbolt-3 and USB-C use the same connector.  To get USB 3 you need a Thunderbolt (not Thunderbolt-3) dock with USB 3 connectors."

Am I misunderstanding, or does this mean that the adapter is not going to help me?

Thanks again (Confused)

This is going to be a daft question, but if i have usb 2.0 device and connect it to a usb female to thunderbolt male adapter and of course plug that adapter into a thunderbolt port on my mac, will it increase my transfer speed? Or will my speed remain at the usb 2.0 default of 480

Your maximum speed would be the USB 2.0 speed.  When connecting with adapters, your speed will be limited by the this case it's USB 2.0.

I have a single PC with a Thunderbolt 3 port and I have multiple devices that are USB-C *Gen 2* capable of 10gbps.

Questions: I would like to purchase ONLY Thunderbolt 3 cables and use them versus buying two different cables and having to select between the two? (A) will this work? (B) If yes, I'm sure my Thunderbolt 3 devices will perform to spec but will my USB-C *Gen 2* devices perform to spec using the Thunderbolt 3 cable? 

If you have a good quality Thunderbolt 3 cable, then your USB 3.1 gen 2 devices should also be support and purchasing different cables wouldn't be necessary.  Theoretical transfer speed for Thunderbolt 3 is 40Gbps and USB 3.1 gen 2 theoretical speed is 10Gbps so your devices will work just fine.

This doesn't make any sense ---> You wrote: "New USB Type-C connectors will also be directional, but that function will only be available with Thunderbolt host ports."

USB has ALWAYS been directional, Thunderbolt taking advantage of the port or not.  And, if the function of it being limited to directional is available ONLY to Thunderbolt, how screwed up will the new Type-C port be without Thunderbolt???  I can only assume it is bi-directional, if using a Thunderbolt port, which is not what you state, but that is my guess.

Please clarify, this statement is very unclear.

great article! now for the magic question. what's the story with cables? you see different lengths and supposedly transfer rates for usb-c and thunderbolt. does the cable matter or is usb-c usb-c for any speed? is thunderbolt the same?



USB-C is really just the port, a place on your computer and device to plug into.  Different technologies can go through the port such as Thunderbolt, display, USB 3.0, ethernet, and/or just charging your device.  And it's really up to the manufacturer so you'd have to really look into the specs and features.  For example, a PC has a USB-C port but only supports USB 3.0 through this port.  You wouldn't purchase a USB-C Thunderbolt 3 cable.  Instead you'd just purchase a USB-C USB 3.0 cable.

My laptop is not thunderbolt three compatible, I was wondering if there was some hardware I could install to make it thunderbolt compatible. I have looked every where can't seem to find a way. 

There aren't any adapters or hardware which would enable Thunderbolt compatibility on your laptop.  The Thunderbolt technology would have to be built in to your computer's motherboard.  Laptops without this feature would not be able to use Thunderbolt.

Very informative article.  I have a question.  I'm thinking about buying one of the 2016 MacBook Pros that B&H has on sale.  These have usb-c ports only.  I have a Thunderbolt display, about 5 maybe 6 years old, with Thunderbolt 2.  Would the new MacBook drive this display?  Thanks

Hi Gregory.  Yes, it would work.  You would just need the Apple Thunderbolt 3 to Thunderbolt 2 adapter.  Please see the link below.

This was very helpful, though I still have a question. Can a thunderbolt to thunderbolt cable be used to connect a thunderbolt port to a usb-c port? I recently aquired the HP Spectre 360 15.6". The right side has a usb-c port and a usb-c thunderbolt port. Due to use of several peripherals I needed a docking station. The docking station I selected had a usb-c port to connect to the host device. I am wondering if I can use either the usb-c or thunderbolt port on the Spectre to connect to the usb-c port on the docking station? Or do I specifically need to use the usb-c on the Spectre to the usb-c on the docking station. My goal is to use the connection that will allow me to power the Spectre while utilzing ethernet connection via the ethernet port on the hub and also to have available the highest data transfer speeds possible

I bought a Vantec SSD card reader which ended up being a Type-C adaptor and my iMac doesn't have a type-c input. I can't seem to find an adapter to remedy my problem. Can anybody lend a hand?

Hi Jason -

The Apple Lightning Male to USB Type-C Male Cable connects your iPhone, iPad, or iPod with a Lightning connector to your computer's USB Type-C port for syncing and charging. You can also use the cable with an Apple 29W USB Type-C Power Adapter to take advantage of the fast charging feature on the 12.9" iPad Pro.

If you plug a USB 3.0 port into a Thunderbolt 3 port (using an adapter), will that increase the bandwitdth available to each port, vs plugging the hub into a USB 3.0 port?  I've got a new iMac on the way (from B&H), and am in the process of thinking-through how to set it with my periphals, using USB 3.0.

I meant "..plug a USB 3.0 *hub* into a Thunderbold port..." :)

You are always limited to the slowest common denominator. In this case it would be the single USB 3.0 cable into the Thunderbolt adapter, providing a maximum bandwidth of 5Gbps that would be distributed to the ports on your hub. 

I have older USB 2.0 and 3.0 devices such as printer, scanner, fan, etc.  Will I be able to plug into a thunder bolt slot?  If not, can I adapt?  If so, how will it work?

You would need an adapter.  The adapter would depend on which Thunderbolt port your computer is equipped with.  If your computer has Thunderbolt 1 or Thunderbolt 2, then you would need this adapter along with a USB hub.

If your computer has Thunderbolt 3, then you can just purchase a USB type-C adapter to USB type A hub such as this one.

  1.  Apple was the first mainstream adopter of USB (eg. iMac) and effectively popularized the standard. However, to provide the playground of multimedia creativity they tout, a faster technology was inherently needed for Digital AV mediums/interfaces at that time (eg. FireWire for SD/HDV,SMPTE 259M).
  2. It seems (to me) like eons have passed since my first Styx cassette...sometimes I miss the simplicity of "push'n'play", as well. That being said, I know how easy it is to dislike the iGeneration for their absence in the evolution of the digital age, is our generation that has created quasi-plug'n'play interfacing. I can only hope the future includes a global standard, agreed on by all manufacturers! Wasn't that the purpose of USB? :P

My Tandy 2000 from 1985 had USB, but was useless in 1985. It was not till Windows 98 that USB had driver support and became popular.

The USB standard wasn't even finalized until the mid 90s. I think your recollection of a 1985 PC having USB has to be inaccurate. I'm pretty sure the T-2000 had a custom serial interface, but it wasn't USB.

Nope, definitely not. No USB interface on the original Tandy's and doubtful anyone could've modified the boards etc. to accommodate USB circuitry, without a complete change-out of the guts.

We used to laugh at those Tandy's. Business professionals thought they were the next Nixdorfs.

Wow, good memories. I developed some of my first software packages for the tech sector on one of those 80186 machines. better resolution graphics, better processor; it was a lot more machine when everything else around it was 'just a pc.'

That's impossable, i think you are thinking of somthing else

You should check your facts better. USB 3.0 and up is most definitely bidirectional.

only type c

I recently purchased a iMac that has Thunderbolt 2.  I would like to purchase a dock to manage my external drives and my big screen HDMI..  I did not realize that this would be such a large expense.  I have noticed that the USB-C dock are considerably less expensive.  My question is can I use a USB-C dock with my iMac?  Will I still have the same speed advantages?

Thank you

If the USB-C dock you are looking into is Mac compatible, it shouldn't be a problem if you have the Thunderbolt 3 to Thunderbolt 2 adapter.  You won't have the Thunderbolt 3 bandwidth but Thunderbolt 2 speeds should be more than enough.  

Thunderbolt 3 to Thunderbolt 2 dock

I'm developing a USB3.1 Gen1 sensor that transmits ~300-350MBps.  In my application, I can have 4 of these sensors operating simultaneously. Can I use a Thunderbolt 3 host with a USB3.1 hub to get 300MB on each port (each sensor)?  If now, how would you suggest I get 4 sensors sending this data into a Thunderbolt 3 host? How can I daisy chaing these USB 3.1 devices on Thunderbolt 3 ?

My current option is to put a 4 port USB3.1 card into a PCIe slot where each port contains a dedicated xHCI controller.  I would like to use the new intel NUC Skull Canyon, which has a Thunderbolt 3 port.


You would not be able to use a hub as you would be limited in bandwidth to a single USB port. We do not currently offer a device that would let you chain Thunderbolt 3 with USB 3.1 Ports. The best option at this time would be a PCIe card as you described. 

Well, I want to know basically, if I can buy an external Thunderbolt 3 interface drive that is 40Gbps and connect it to a new card I added in my desctop that give me USB 3.1 Type-C  (same plug as thunderbolt 3) the dodocool PCI-Express Card with Dual Type-C Ports 15-Pin Connector SuperSpeed Gen II (10 Gbps)

What I don't get is how are they going to make USB 3.1 Type-C to be 40Gbps as fast as Thunderbolt 3. Through firmware. it is about time that USB 3.1 Type-C  AND Thunderbolt 3 finally are merging, but how is the USB 3.1 Type-C going to reach the 40Gbps speed. Am I ok connecting a Thunderbold 3 ext. HDD like Pegasus or Glyph to the  USB 3.1 Type-C input port of my desktop. I assume if this is possible I will expect 10Gpps speed, since the drive might be Thunderbolt 3 but the bottle-neck is the USB 3.1 Type-C port



USB 3.1 and Thunderbolt 3, while sometimes using the same port, are different protocols. Not all USB-C ports will be 3.1, or Thunderbolt compatible. If you purchased a drive that is Thunderbolt 3, and your port is USB-C with USB 3.1 support only, the Thunderbolt drive will not be recognized. Your USB-C port MUST also support Thunderbolt 3 to user Thunderbolt devices. 

So to clarify, I was looking at two MSI laptops, GE72VR and GS73VR with the plan of running an external gpu through Razer or comparable Thunderbolt 3 peripheral.  According to specs below, GE72VR has a USB 3.1 Type-C port, while the GS73VR has a Thunderbolt 3 port.  By the delineation, I assume that means the GS73VR would accept a Thunderbolt 3 with total functionality, and the GE72R would not recognize it and render it useless.  Is my thinking correct?

> if I can buy an external Thunderbolt 3 interface drive that is 40Gbps

When you plug a Thunderbolt 3-based storage drive into your computer, you'll have a 40 Gbit/s connections between your system and the storage device. However, the hard drive inside of that device is still limited to at most 205 MB/s.​ ... Thunderbolt 3 does NOTHING for you here.

Are you in 2011? Single SSD drives are 480 Mbps, raid arrays can reach 4.5 Gbps. 

Notice I wrote 480MB/s (megabytes per second ) not 490mb/s (megabits per second). 40Gb/s is roughly 4GB/s or 4096MB/s. So ... yeah, that RAID is almost 10 times slower than the TB3 connection.

Are you always rude when responding to comments?

Sigh! That should have been:

So ... yeah, that SDD is almost 10 times slower than the TB3 connection.