Thunderbolt 4 Alt Mode over USB-C is identical to TB3 electrically but with stricter certification requirements: guaranteed 40 Gbps, minimum dual 4K display support, Intel VT-d based DMA protection, and wake from sleep.
| Pin | Name | Function | Type |
|---|---|---|---|
| A1 | GND | Ground | GND |
| A2 | TX1+ | TB4 TX lane 1 positive | BUS |
| A3 | TX1- | TB4 TX lane 1 negative | BUS |
| A4 | VBUS | Power up to 100W | PWR |
| A5 | CC1 | Config channel 1 TB4 negotiation | BUS |
| A6 | D+ | USB 2.0 D+ | BUS |
| A7 | D- | USB 2.0 D- | BUS |
| A8 | SBU1 | Sideband use 1 | BUS |
| A9 | VBUS | Power | PWR |
| A10 | RX2- | TB4 RX lane 2 negative | BUS |
| A11 | RX2+ | TB4 RX lane 2 positive | BUS |
| A12 | GND | Ground | GND |
| B2 | TX2+ | TB4 TX lane 2 positive | BUS |
| B3 | TX2- | TB4 TX lane 2 negative | BUS |
| B5 | CC2 | Config channel 2 | BUS |
| B8 | SBU2 | Sideband use 2 | BUS |
| B10 | RX1- | TB4 RX lane 1 negative | BUS |
| B11 | RX1+ | TB4 RX lane 1 positive | BUS |
Thunderbolt 4 Alt Mode over USB-C is identical to TB3 electrically but with stricter certification requirements: guaranteed 40 Gbps, minimum dual 4K display support, Intel VT-d based DMA protection, and wake from sleep.