Computer won't start with 4 RAM modules

[zan.gerden.kom]

Hello,

Before I upgraded PC, my specs were:
- AMD FX-4100
- Asus Sabertooth 990fx R2.0
- Silent Pro 1200W
- AMD HD7970
- Kingston KHX1600C9AD3B1/2G
- Corsair CMV4GX3M1A1333C9
- G.Skill F3-10666CL9S-2GBNS
- Corsair CMZ4GX3M1A1600C9

With that, everything worked perfectly, but when I upgraded PC to:
- Intel i7-3770
- Asrock B75 Pro-3M
- Everything else is same
- Used RAM:
• Corsair CMZ4GX3M1A1600C9
• Corsair CMV4GX3M1A1333C9

I couldn't fit all RAM's into motherboard, no matter what combination I used - it seems that maximum of 2 RAM's can be in that motherboard.
So, I would like to ask you for any ideas, what could I do... Also, I updated BIOS to latest version.

Edit: Forgot to mention, computer wont POST (it makes 4 short beeps and then restarts) if there are more than 2 RAM's in motherboard.

 

[Kasper Jorgensen]

Mixing up RAM can cause compatibility issues, which is most likely what is happening here. Get a new RAM kit. Changing motherboard could mean that what worked before, no longer works.

 

[zan.gerden.kom]

Okay, so I found solution - I don't know why, but it works.
First I tried putting bot 1600 RAM into A1 and A2 slot which worked, and then in BIOS I noticed that it's running on 1333MHz, so I switched it to 1600MHz. After that worked, I tried putting other RAM into B1 and B2 slots, and then everything started working as supposed, except that slower RAMs are apparently running at 1600MHz. Anyway, I won't complain since computer is stable and works