Windows 8 supports TPM 1.2 for Bitlocker, for secure boot TPM must comply with the TCG TPM Main Specification, Version 1.2, Revision 103 (or a later), parts 1, 2 and 3. For more information, see the article
Windows 8 Hardware Certification Requirements.
The difference between Discrete TPM and Firmware/Software TPM is that a Discrete TPM is a own chip on the motherboard, a Firmware TPM is integrated on some other components on the motherboard.
You can use some security features like bitlocker without a TPM but it's not that secure.
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