Asus TW100-E5 iQuadro - Manual (Page 50)

Chapter 3: Motherboard information 3-10
3. Optical drive audio connector (4-pin CD)
These connectors allow you to receive stereo audio input from sound sources
such as a CD-ROM, TV tuner, or MPEG card.
4. TPM connector (20-1 pin TPM)
This connector supports a Trusted Platform Module (TPM) system, which can
securely store keys, digital certificates, passwords, and data. A TPM system
also helps enhance network security, protects digital identities, and ensures
platform integrity.
The TPM module is purchased separately.