PC Freeze HD7970 crossfire

When i play games(asseto corsa, COD aw, Grid 2, Lol(only in win 8.1)) my screen freezes, speekers make buzzing noise and i need to reset my pc.

My trouble shooting:
reinstall Amd drivers.
switch OS from win 8.1 back to Win7(this helpt a litle).
when card 2 is in slot 1 (only 1 card) at 16X pc won't post
analyse crash dumps found driverproblem Fixt it but the problem wasn't resolverd.

pc specs:
windows version: Windows 7 Service Pack 1, 6.1, build: 7601
windows dir: C:\Windows
CPU: GenuineIntel Intel(R) Core(TM) i5-4670K CPU @ 3.40GHz Intel586, level: 6
4 logical processors, active mask: 15
RAM: 8515878912 total
VM: 2147352576, free: 1917931520

amd software:
Driver Packaging Version 14.501.1003-141120a-177998C
Catalyst Version 14.12 AMD Catalyst Omega Software
Provider Advanced Micro Devices, Inc.
2D Driver Version 8.01.01.1443
2D Driver File Path /REGISTRY/MACHINE/SYSTEM/ControlSet001/Control/CLASS/{4D36E968-E325-11CE-BFC1-08002BE10318}/0001
Direct3D Version 9.14.10.01080
OpenGL Version 6.14.10.13283
Mantle Driver Version 9.1.10.0045
Mantle API Version 98304
AMD Catalyst Control Center Version 2014.1120.2123.38423
AMD Audio Driver Version 7.12.0.7719

Hardware:
Card 1:
Graphics Card Manufacturer Powered by AMD
Graphics Chipset AMD Radeon HD 7900 Series
Device ID 6798
Vendor ID 1002
Subsystem ID 3212
Subsystem Vendor ID 1682
Revision ID 00
Graphics Bus Capability PCI Express 3.0
Maximum Bus Setting PCI Express 3.0x8
BIOS Version 015.022.000.004
BIOS Part Number 113-797ATDFV33_111215SZ
BIOS Date 2012/07/15
Memory Size 3072 MB
Memory Type GDDR5
Core Clock in MHz 925 MHz
Memory Clock in MHz 1375 MHz
Total Memory Bandwidth in GByte/s 264,0 GByte/s

Card 2:

Graphics Card Manufacturer Powered by AMD
Graphics Chipset AMD Radeon HD 7900 Series
Device ID 6798
Vendor ID 1002
Subsystem ID 3212
Subsystem Vendor ID 1682
Revision ID 00
Graphics Bus Capability PCI Express 3.0
Maximum Bus Setting PCI Express 3.0x8
BIOS Version 015.022.000.004
BIOS Part Number 113-797ATDFV33_111215SZ
BIOS Date 2012/07/15
Memory Size 3072 MB
Memory Type GDDR5
Core Clock in MHz 925 MHz
Memory Clock in MHz 1375 MHz
Total Memory Bandwidth in GByte/s 264,0 GByte/s


thanx for your help