Cannon Lake seems to be intended for energy-efficient systems, whereas Coffee Lake will target the more power hungry models.
You can see that the CFL-H processors will have a 45W TDP and 6C configuration, while the lower power 15/28W CFL-U chips will be limited to 4C parts. Above you can see BenchLife claims that the desktop Coffee Lake Core (DT CFL-S) processors will be made available in both 6C and 4C configurations.The 14nm six-core Coffee Lake is expected to measure 149mm², while the quad-core models will not have cores disabled but will be purposely designed parts with a size of 126mm². The slides also reveal plans for an enthusiast-class Coffee Lake X platform, but there are even less details about that chip.
The new platform will go further along the integration road, with new interfaces and connectivity stuffed in the chipset. Thus it is expected that Coffee Lake S processors won't be compatible with earlier motherboards and sockets.
Via: Hexus