Broadwell (5th-gen) devices:
- 13v1 - has pop-up ethernet port
- 15v2
Skylake (6th-gen) devices:
- 13v2 (few late devices have TPM, switches on hinge)
- 13v3 (all devices have TPM, switches on side)
- 15v3 (some devices have TPM)
completely new board/chassis design from 5th-gen
improved multi-touch trackpad
adds USB-C port
Kabylake (7th-gen) devices:
- 13v4
- 15v4
all devices have TPM
same board as 6th-gen devices, just upgraded SoC
15v4 has 4K display