DRAM related post failure

[sa1672ndo]

PC fails to post if 2x4gb memory sticks are mixed with 1x8gb.

Configurations I tried

2x4 on A1 and B1 slots(posted without any issues)

1x8 on A1 slot(posted without any issues)

2x4 on A1 and B1 with 1x8 on A2 (no post, even with "memOK" function)

1x8 on A1 with 2x4 on A2 and B2 (no post, even with "memOK" function)

All of the sticks are 1600mhz but 1x8gb is made by a different brand than the 2x4gb

Specs

 

CPU:intel i5 3470

 

Mobo: p8b75-m

 

GPU:sapphire rx 560 nitro

 

Psu: thermaltake TR2 500W S series

 

Ram: 2x4gb ddr3 1600mhz (silicon power) and

1x8 ddr3 1600mhz (sk hynix)

[sa1672ndo]

PC posted after I re-seated them like 5 times