I was encrypting a hard drive with VeraCrypt using AES, about 1 TB, which takes a few hours. My computer has an Intel i5 6500 with AES-NI (hardware accelerated AES). I noticed the CPU frequency went down from 3.2 GHz (base clock) to around 0.9 GHz, as is usual with power saving features these days, and the task manager shows idle usage at 5-15%.

Is the speed of the encryption in any way dependent on the CPU frequency, i.e. could I speed up this process by switching the power saving mode in my operating system (Windows) to "maximum performance"?

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    Check diskI/O in taskmgr; you'll probably find it's maxed out, and if so increasing the CPU speed would not give any benefit. – dave_thompson_085 Apr 14 '19 at 5:57

Is AES-NI processing speed influenced by CPU frequency?

Not in the context of disk encryption.

A modern processor with AES-NI can encrypt/decrypt data at well over 1 GB/sec. This is significantly faster than most SSDs, let alone a hard disk -- your CPU is sitting around twiddling its thumbs while it waits for your hard disk to read and write the data that's being encrypted.

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  • Yes it is true that the HDD is at near its maximum load, not even close to 1 GB/sec. Ignoring the HDD speed and (USB 3 / SATA) bandwidth constraints, does AES speed depend on CPU speed at all? – chrki Apr 14 '19 at 12:37
  • It seems that, yes, CPU frequency does influence AES speed with my computer setup. Running the Veracrypt benchmark tool with a big payload runs the CPU at 100% at and above base clock. – chrki Apr 14 '19 at 18:52

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