Some processors (CPUs) support hardware-accelerated AES encryption,* which is typically 4-8 times faster than encryption performed by the purely software implementation on the same processors.
By default, TrueCrypt uses hardware-accelerated AES on computers that have a processor where the Intel AES-NI instructions are available. Specifically, TrueCrypt uses the AES-NI instructions that perform so-called AES rounds (i.e. the main portions of the AES algorithm).** TrueCrypt does not use any of the AES-NI instructions that perform key generation.
Note: By default, TrueCrypt uses hardware-accelerated AES also when an encrypted Windows system is booting or resuming from hibernation (provided that the processor supports the Intel AES-NI instructions).
To find out whether TrueCrypt can use hardware-accelerated AES on your computer, select Settings >Performance and check the field labeled 'Processor (CPU) in this computer supports hardware acceleration for AES'.
To find out whether a processor you want to purchase supports the Intel AES-NI instructions (also called "AES New Instructions"), which TrueCrypt uses for hardware-accelerated AES, please check the documentation for the processor or contact the vendor/manufacturer. Alternatively, click here to view an official list of Intel processors that support the AES-NI instructions. However, note that some Intel processors, which the Intel website lists as AES-NI-supporting, actually support the AES-NI instructions only with a Processor Configuration update (for example, i7-2630/2635QM, i7-2670/2675QM, i5-2430/2435M, i5-2410/2415M). In such cases, you should contact the manufacturer of the motherboard/computer for a BIOS update that includes the latest Processor Configuration update for the processor.