MSI X299-A Pro Quick Start Manual page 27

Memory module installation recommendation (2-Channels architecture CPU )
B1 B2
1 DIMM
2 DIMMs
3 DIMMs
4 DIMMs
DIMMB1, B2, A1 and A2 are un-available
A1 A2 Intel Core X-series CPU
Supports 2-channels
memory architecture
DIMMC1
DIMMC2
DIMMC1
DIMMD1
C2 C1 D2 D1
DIMMC1
DIMMD1
DIMMC2
DIMMC1
DIMMD2
DIMMD1
Overview of Components
17