My apologies for this late reply.
Please check whether “lspci | grep VGA” command shows the integrated GPU one or not. Otherwise, it might have been disabled and needs to be enabled from the BIOS.
[root@Machine ~]# lspci | grep VGA
00:01.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] Kaveri [Radeon R7 Graphics] (rev d4)
03:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] Vesuvius [Radeon R9 295X2]
05:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] Cypress XT [Radeon HD 5870]
[root@Machine ~]# aticonfig --list-adapters
* 0. 03:00.0 Supported device 67B9
1. 04:00.0 Supported device 67B9
2. 05:00.0 AMD Radeon HD 5800 Series
I have enabled integrated GPU in BIOS and have chosen it as the first output device but no luck.
The machine installed dual OS, Windows 10 and CentOS 7. On both OS, the graphics driver shipped with OS works well for integrated graphics output. After installing the AMD proprietary driver, the output automatically changed to discrete PCI-E card and it seems no way to change back. Now the machine outputs on integrated GPU before OS finishing boot, and outputs on discrete GPU after OS reaching login screen: it is unconvenient for dual OS switch.
I'm still hunting for the solution. I've asked few folks regarding the problem but haven't got any definitive answer yet . I need few inputs from you.
1) Did you try to reinstall the driver freshly?
2) If you run the "clinfo" command, do you see all the cards? Or "clinfo" also lists the same gpus as "aticonfig --list-adapters" command
3) Can you please check the commands in console mode (without X) and share your findings?
4) Whether removing any card showing the integrated GPU or not?
Install latest AMD Catalyst™ 15.7 Proprietary Linux x86 Display Driver, the problem is gone! @dipak