Differences Between Thunderbolt 3 and Thunderbolt 4

                                             Differences Between Thunderbolt 3 and Thunderbolt 4

Currently, Thunderbolt 3 offers a maximum data rate of 40 Gbps and can support two 4K displays at 60 Hz simultaneously.
Although Thunderbolt 4 maintains the same maximum speed of 40 Gbps, it brings five major upgrades compared with Thunderbolt 3:

1. Video Output – The minimum PC video specification is doubled. Supporting two 4K displays or one 8K display is now a baseline requirement, whereas Thunderbolt 3 devices might only support a single 4K display at minimum.

2. PCIe Bandwidth – The minimum PC data requirement for PCIe is doubled from 16 Gbps to 32 Gbps, enabling storage speeds of up to 3 GB/s—much closer to the performance of an internal motherboard connection.

3. Docking Expansion – For the first time, Thunderbolt 4 supports docks with up to four ports and cable lengths of up to 2 meters, allowing a single cable to branch into three Thunderbolt 4 ports, enabling the connection of multiple devices simultaneously.

4. Charging Support – A Thunderbolt 4 PC must have at least one port capable of charging devices.

5. Wake from Sleep – When connected to a Thunderbolt dock, the computer can be woken from sleep via a keyboard or mouse.

Key Technical Comparisons:

• Data Transfer Rate – Thunderbolt 4 still delivers 40 Gbps, the same as Thunderbolt 3.

• PCIe Data Throughput – PCIe bandwidth increases from 16 Gbps to 32 Gbps, allowing storage transfer speeds of around 3000 MB/s and even meeting the needs of some mid- to high-end external GPUs.

• Video Transmission – Upgraded to support either dual 4K resolution or a single 8K resolution output—particularly beneficial for design professionals using laptops.

• Additional Enhancements – Support for docks with up to four Thunderbolt 4 ports; mandatory charging capability on at least one port; wake-from-sleep via peripherals; and required Intel VT-d–based DMA (Direct Memory Access) protection to prevent physical DMA attacks.

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  Thunderbolt 3 vs Thunderbolt 4 comparison table :

  Feature	Thunderbolt 3	Thunderbolt 4	Quick Takeaway
  Max Data Transfer Rate	40 Gbps	40 Gbps	No speed change—performance parity.
  Minimum PCIe Bandwidth	16 Gbps	32 Gbps (up to 3 GB/s)	Double the PCIe speed for faster storage & eGPU use.
  Video Output (Minimum Spec)	At least 1 × 4K display	2 × 4K displays or 1 × 8K display	Higher guaranteed video capability.
  Dock Support	Up to 1 downstream TB port	Up to 4 downstream TB4 ports	Connect more devices from one dock.
  Max Cable Length (Full Speed)	~0.5 m (passive)	Up to 2 m at 40 Gbps	Longer cables without losing speed.
  Device Charging Requirement	Not mandatory	At least 1 port must charge devices	Guaranteed charging support on laptops.
  Wake from Sleep via Peripherals	Not guaranteed	Required	Wake PC with the mouse/keyboard from the dock.
  Security	Optional DMA protection	Mandatory Intel VT-d DMA protection	Stronger protection against DMA attacks.
  Backward Compatibility	Works with TB1/2/USB	Works with TB1/2/USB/TB3	Full compatibility with all TB generations.

  
  

• In summary, Thunderbolt 4 primarily improves compatibility, reliability, and security while enhancing connectivity. It can be seen as a refined and more versatile extension of Thunderbolt 3 rather than a radical speed upgrade.