How to switch between 2 GPUs present in same system?

Firstly i am new to work with the GPUs so please correct me if i am wrong. I have an HP-z440 box with 2 GPU cards **

1. AMD/ATI Firepro W2100
2. AMD/ATI Firepro W5100

**
I am working on SLES 12 OS I have installed the appropriate drivers form the HP official site.

    linux:~ # lspci -v | grep -A 15 VGA
02:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] Oland                                                                                         GL [FirePro W2100] (prog-if 00 [VGA controller])
        Subsystem: Hewlett-Packard Company Device 2120
        Physical Slot: 2
        Flags: bus master, fast devsel, latency 0, IRQ 94
        Memory at d0000000 (64-bit, prefetchable) [size=256M]
        Memory at f0d00000 (64-bit, non-prefetchable) [size=256K]
        I/O ports at 2000 [size=256]
        Expansion ROM at f0d60000 [disabled] [size=128K]
        Capabilities: [48] Vendor Specific Information: Len=08 <?>
        Capabilities: [50] Power Management version 3
        Capabilities: [58] Express Legacy Endpoint, MSI 00
        Capabilities: [a0] MSI: Enable+ Count=1/1 Maskable- 64bit+
        Capabilities: [100] Vendor Specific Information: ID=0001 Rev=1 Len=010 <                                                                                        ?>
        Capabilities: [150] Advanced Error Reporting
        Capabilities: [200] #15
        Capabilities: [270] #19

03:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] Bonair                                                                                        e [FirePro W5100] (prog-if 00 [VGA controller])
        Subsystem: Hewlett-Packard Company Device 0b0c
        Physical Slot: 5
        Flags: bus master, fast devsel, latency 0, IRQ 93
        Memory at e0000000 (64-bit, prefetchable) [size=256M]
        Memory at f0000000 (64-bit, prefetchable) [size=8M]
        I/O ports at 1000 [size=256]
        Memory at f0c00000 (32-bit, non-prefetchable) [size=256K]
        Expansion ROM at f0c60000 [disabled] [size=128K]
        Capabilities: [48] Vendor Specific Information: Len=08 <?>
        Capabilities: [50] Power Management version 3
        Capabilities: [58] Express Legacy Endpoint, MSI 00
        Capabilities: [a0] MSI: Enable+ Count=1/1 Maskable- 64bit+
        Capabilities: [100] Vendor Specific Information: ID=0001 Rev=1 Len=010 <                                                                                        ?>
        Capabilities: [150] Advanced Error Reporting
        Capabilities: [200] #15

and

   Linux:~#` aticonfig --odgc
    
    Default Adapter - AMD FirePro W2100 (FireGL V)
                                Core (MHz)    Memory (MHz)
               Current Clocks :    300           300
                 Current Peak :    680           900
      Configurable Peak Range : [300-1000]     [300-1000]
                     GPU load :    0%

~

I think only 1 GPU card is working at a time. I want both the GPU cards to work, is it possible? Or at least I want to switch between these cards.

Generally speaking, connecting two different graphic cards is not recommended, and probably won't function as expected. For AMD GPUs, you must connect both cards with a "Crossfire Bridge":

It's a small and wide cable that should come in the box with the GPU. There's also a setting to turn Crossfire on and off in the driver software, but it should be on by default.

In order to switch between cards, just plug your monitor into the card of choice.