I am not familiar with linux or  openSUSE Leap 15.2, but I think getting video from the discrete video card is a low level task that should be accomplished during POST before pc goes to boot the OS.  Since you have already made quite a few changes in bios, I suggest you clear CMOS settings to default and remove hdd/ssd from pc, then try to get video from card during POST.  you can either reset cmos jumper or remove/replace cmos battery (after draining system power).

Stock MT power supply is not sufficient to run a 7850.

CX450 is too small for a 7850.

BARE Minimum that would work would be EVGA 700BR

Power supplies have more than 1 rail and more than a single spec of WATTS.

You need BARE MINIMUM 25 AMPS on the 3.3v and 5v rails with BARE MINUMUM 150W combined power on those rails.

https://www.bestbuy.com/site/evga-700w-atx12v-eps12v-80-plus-bronze-power-supply-dc-dc-technology-black/6346160.p?skuId=6346160

Thats why EVGA 750B1 model works fine but the B2 G2 BQ N1 W1 versions do not work from the same vendor.

750W is not a spec its the overall max output.

Dell 850W units have 225W combined on the 3.3v rails and 30 AMPS.

Hi @jaycee99,

If you mention the CPU you have, unless you did already. we can also check bottleneck.

Bottle check?   There's No "I" In Beer - Brad Paisley  We're all in this together.

Indeed. One must use  only  EVGA 700BR

And also do the new bottle check.

Then it's cool.

Hi @bradthetechnut 

Sure, this is my cpu, an i5-3570.  If I'm not mistaken the most powerful i5 CPU that works with the Q77 chipset of the motherboard. 

CPU:       Topology: Quad Core model: Intel Core i5-3570 bits: 64 type: MCP L2 cache: 6144 KiB  
          min/max: 1600/3800 MHz

Hi @speedstep , 

Recommend PSU for this card is 350W ( https://www.techpowerup.com/gpu-specs/radeon-hd-7850.c1055 )

CX450 is a 450 W PSU, which is 100 W (or 28%) extra.  The 225W PSU of DELL was sufficient to feed the mobo in its original configuration. I did not connect the dvd writer in the current configuration anymore and added 1 SSD.  Thus I added 225W on the PSU only for the 130W this card is demanding. Should be more than enough, no?  

Could you elaborate on the AMPS please? I don't find this kind of specifications.  

Your graphic card is too weak for this processor.

Intel Core i5-3570 (Clock speed at 100%) with AMD Radeon HD 7850 (Clock speed at 100%) x1 will produce 100% of bottleneck. Everything over 10% is considered as bottleneck.

Graphic card and processor will work great together

Intel Core i5-3570 (Clock speed at 100%) with NVIDIA GeForce GTX 1050 Ti(Clock speed at 100%) x1 will produce only 2.23% of bottleneck. 

Graphic card and processor will work great together

Intel Core i5-3570 (Clock speed at 100%) with AMD Radeon RX 470 (Clock speed at 100%) x1 will produce only 3.05% of bottleneck.

Graphic card and processor will work great together

Intel Core i5-3570 (Clock speed at 100%) with AMD Radeon RX 570 (Clock speed at 100%) x1 will produce only 0.24% of bottleneck.

I

Hi @redxps630,

You know how speedstep regularly recommends the 30w GT 1030?  With the Intel Core i5-3570, if PC-Builds says 100% bottleneck and GPUCheck says less 8%, which one would you believe?

gpu check often paints a unrealistic rosy pic of cpu and gpu.  I trust pc-builds more based on prior experience its calculation result is more in line with intuitive estimate.

hi @redxps630 

I put in my even older Radeon HD5750. This is a PCI Express v2 bus, whereas the HD7850 is a PCI Express v3 .  This older cards works, but before the desktop switches to the external video card, it takes ages.  I do not see the BIOS start up, neither do I see my OS loader.  

So, my assumption is that the mobo and BIOS have a hard time detecting a PCI Express v3 external video card (or do not even support it).  

Hi @redxps630 

See my previous reply, where I prove that an even weaker graphics card (Radeon HD 5750) works well with this CPU.  So, IMO, this cannot be the cause for this error.  

never mind the previous bottleneck calculator result. I agree bios is acting up.

reset CMOs jumper to clear settings then try again.  For some reason amd cards are a bit more finicky than nvidia.  If still no luck bios needs to be refreshed, consider update bios but understand risk of bios flash beforehand.

hi @redxps630 

I will try this again. With the previous card, after resetting it didn't work out, perhaps that with this one it does.  Once I get into the BIOS settings again, I can indicate that the AMD card is the main one, instead of leaving it on "auto".  Otherwise, re-install BIOS could be the last option.  

If it does have anything to do with BIOS acting up, unless it was replaced within the last 5 yrs., I'd try a new size 2032 CMOS battery.  The 7010 goes back to 2012-2014.  A low battery will cause all sorts of bizarre problems that seem unrelated.  A CMOS reset won't do any good with a low battery.  Cheap fix even if by chance it doesn't work.

Even with a low battery, indeed, things can still be set in BIOS.  But problems will still develop.