You might have heard the Nexus 6 is sort of slow in many benchmarks. By default, it ships with an encrypted file system which while is secure and all, slows things way down.
Denver uses the ARMv8 architecture, which has native AES and SHA support as part of its instruction set. The Snapdragon 805, meanwhile, achieves its own hardware-level AES support using a proprietary cryptographic module developed by Qualcomm.
My strong suspicion is that these two solutions were not created equally. Qualcomm’s processor roadmap has struggled to make the leap to ARMv8-based chips at the high end of the market, with the company having shifted much of its current release schedule to push 64-bit mid-range and low-end chips in Asia and Europe. Though those chips are using the ARMv8 instruction set, their cores are based on standard ARM reference designs. Meanwhile, the top-tier Krait core still uses ARMv7, thus pushing Qualcomm into offering some form of hardware encrypt/decrypt while its next-gen 64-bit core is still in development.
The behemoth of the mobile processor industry is to blame. Don’t worry, I’ll hold it against them for you.