[HELP] Enabling ATI Radeon HD 5450 on Sony vaio

Hi,
I have a problem with my ATI Radeon HD5470 and Sierra macOS
The macOS recognize the model of graphics fine but i have only 4mo
Everything works except that ...
- I use a Sony Vaio laptop (VPCEB1E8E)
- Product name : MacBookPro 8,1
- I have not changed kexts (AMD5000ctrl & AMDRadeonX3000)

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[HELP] Enabling ATI Radeon HD 5450 on Sony vaio