Active vs Passive Thunderbolt Cables

Are you trying to decide between active and passive Thunderbolt cables? Here’s what you need to know about the two different cables and find out which type is best suited for your needs.

What are passive cables?

passive-thunderbolt-3 cable
Passive Thunderbolt cables have slower transfer speeds but they are longer and cheaper

When you hear the term “passive cables”, what they’re referring to are, cables that don’t have any active electronic components. These active electronic components help to repeat and amplify the signal. This has two implications:

  1. Passive cables are generally cheaper than active cables
  2. The length of passive cables are limited as the signal may degrade over longer distances.

What are active cables?

You can identify active cables from their transfer speed

Active cables have these little chips inside of them that boosts the signal, increasing the distance that they can travel at high speeds. It’s worth noting that the faster data travels, the faster data degradation occurs. More on that later but what you need to remember about active cables are:

  1. Active cables are more expensive than passive cables
  2. Active cables can transfer data at faster speeds over longer distances than passive cables

Active vs Passive Thunderbolt: Which To Choose?

Let’s say you need to connect your laptop to your docking station. If the distance between them is 0.8 meters (2.6 feet), then a passive Thunderbolt 3 cable will allow you to transfer data at 40 Gbps.

Now, if the distance between your laptop and docking station were to be 2 meters (6.5 feet) instead, a passive Thunderbolt 3 cable would only transfer data at 20 Gbps.  

To transfer data at 40 Gbps, you will need an active cable instead. With its chips to boost the signal along the cable, it increases the distance that can data can travel before degradation occurs.

In the future, there are plans for optical Thunderbolt 4 cables which will extend the length of Thunderbolt 4 cables from between 5 meters (16 feet) to 50 meters (160 feet).

Active And Passive Cables USB Compatibility

Price and cable length will probably be your main considerations when deciding between active and passive cables. One other tricky thing to consider is USB compatibility.

Since Thunderbolt 3, you could use Thunderbolt cables on USB-C ports. However, active Thunderbolt 3 cables only support up to USB 2.0 (480 Mbps) while passive Thunderbolt 3 cables support up to USB 3 (20 Gbps). You would think that it would be the other way around, which results in a lot of confusion.

If you want to avoid the confusion just get Thunderbolt 4 cables. Both active and passive Thunderbolt 4 cables are compatible with USB 4 and support speeds of up to 40 Gbps.  

Final Thoughts

Active Thunderbolt cables do not come cheap and at the point of writing, cost more than double that of passive cables. This is thanks to the extra chips in them that help to boost the signal over longer distances. If you need a Thunderbolt cable over 0.8 meter long, it would need to be an active cable. Over short distances, a passive cable works fine and you can save some dollars by getting one instead. Now that you know the differences between Active and Passive Thunderbolt cables, you might be interested in reading whether Thunderbolt 3 cables are the same as USB-C?

A software engineer, I have a strong interest in technology, bot software and hardware. Blogging is a way to share what I have learned and hopefully people will find it useful.

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