The M8 has a Snapdragon 801 chipset and Quad-core CPU clocked at 2.3GHz (The Asian market gets a 2.5GHz version!), and 2GB of RAM. Clock-speed wise this is a decent step up from the 1.7GHz quad in the M7.
So what does this clock speed jump equate to? In general usage the difference isn’t that noticeable but in intensive apps and games you’ll notice it more.
In the video below you’ll see an HTC One (M8) Benchmark compared to the HTC One (M7). The benchmark was run simultaneously to give some impression of the speed and how much quicker the M8 completed the test.
Interesting results in that the M8 has twice the score of the M7!