M.2 Heatsink
M.2 heatsink wards off throttling that can occur with M.2 storage during sustained transfers. The heatsink is held in place by captive screws.
VRM Heatsink and Thermal Pad
VRM heatsink and thermal pad improve heat transfer from the MOSFETs and chokes for better cooling performance.
DDR4 5333(OC)
Improvements to trace routing design provide the latest Intel processors with enhanced access to memory bandwidth. ASUS OptiMem II technology carefully maps memory signal pathways across different PCB layers to reduce path distance, and it adds shielding zones that significantly reduce crosstalk.
Two M.2 slots (up to 64 Gbps)
Prime B660M-A WIFI D4 offers a total of two M.2 slots that support data-transfer speeds of up to 64 Gbps via PCIe® 4.0, enabling quicker boot-up and app load times with OS or application drives.
* Actual transmission speeds will be lower than the theoretical maximum speed.
Addressable Gen 2 Headers
Three addressable Gen 2 headers are capable of detecting the number of LEDs on second-gen addressable RGB devices, allowing the software to automatically tailor lighting effects to specific devices. The new headers also offer backward-compatibility with existing Aura RGB gear.
Source : Asus PRIME B660M-A WIFI D4