[SOLVED] need help getting a 1080 Ti to work with a legacy motherboard (if it's even possible) (HP Z420)

Dec 7, 2021
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I recently picked up an Asus Founders Edition 1080 Ti, and wanted to put it in my current PC, a Z420 workstation from my dad's old work. Along with the 1080 Ti, I bought a new PSU (a Corsair RM750 2019) to feed the hungrier graphics card. The original HP proprietary mobo takes an 18-pin power connector instead of the standard 24, and the Corsair one came with a 24. So I'm running 2 power supplies, one for the 1080 Ti (the RM750 bc it has the 6+2 along with the regular 6 I needed) and one for the rest of the system (the original one). The mobo does have a PCIe gen3 x16 slot, so I should've just been able to drop the GPU in and have it work (after getting all the drivers and everything). One thing I should mention is that the current BIOS is not UEFI, it's legacy. I heard that could cause issues, but I don't know. There's a way to get it to use a UEFI BIOS, but I haven't tried it yet due to a lack of detailed instructions. The problem is the motherboard doesn't seem to be detecting the card, or can't communicate with it. The GeForce logo lights up on the card and the fans come on, but when I first tried to boot it up the system gave me a beep-blink error code (6 beeps and blinks in a row, then a 2s pause before repeating, which means a "pre-video graphic card error") and didn't appear to boot at all (nothing on my monitor changed, it wasn't getting a source). I pulled the card out, blew out the slot (which was the same one the original GTX 560 was in literally less than 30 min before when I was benchmarking it), blew off the contacts, and put it back in. Same thing. I stuck a fanless VGA display adapter in just to see what was going on, and it booted just fine. The 1080 Ti didn't show up in Device Manager at all, after refreshing it multiple times. I bought the card from a trusted family friend, and I don't think they would knowingly sell me a dead card. I've tried everything my friends and I can think of to no avail (reseating the GPU, switching slots [it didn't fit in the other cuz of the case, not the slot], updating bios, etc). I'm going to test it on a different PC when the last part shows up to make sure it isn't the card itself, but that won't be for another couple of days. I don't have the money to start from scratch with a new mobo, CPU, and RAM (the old motherboard is DDR3) currently, so is there any way I can get this to work? I have practically no experience dealing with legacy BIOSs, so go easy on me.

thanks in advance

edit: forgot to put full system specs, so here they are
CPU: Intel Xeon E5-1620 0
Motherboard: HP 1589, FMB-1101 (it's HP proprietary so I don't know the exact name. UserBenchmark lists it as HP 1589, but the board itself has a sticker on it that says FMB-1101)
Ram: Micron 4x4gb 16gb DDR3 1600mhz (unsure of exact model)
SSD/HDD: 3x1tb seagate barracuda HDD (the silver w/ white sticker, not the green sticker ones)
GPU: Nvidia GeForce GTX 1080 Ti (originally had a GTX 560)
PSU: HP Proprietary 650w (the original one afaik), Corsair RM750 2019
Chassis: HP Z420 stock case
OS: Windows 10 Pro(?) x64 (has lastest update as far as I'm aware, unsure of exact version)
Monitor: generic 1080p 60hz monitor
 
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TommyTwoTone66

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You may be out of luck. Those HP Xeon boards tend to be locked to certain graphics cards in the bios.

There are people who have hacked the bios to unlock them and even add specific hardware to the list of allowed devices, but it is pot luck as to whether you can find a modded or unlocked bios to download for your specific board.
 
Dec 7, 2021
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Here, the issue you have here is the power supply, the card will work fine, it isn't "locked out"
Buy this problem solved.
https://www.amazon.com/Longdex-11-8-Inch-Power-Adapter-Motherboards/dp/B089NM4MK1/ref=sr_1_3?crid=2TY5RZ3REBP4Y&keywords=24+to+18+pin+psu+adapter&qid=1638923628&sprefix=24+to+18+p,aps,219&sr=8-3

I have done so with a hpz220, no problems at all.
edit: i figured it out, thanks for your help

i looked at that when i realized the HP mobo took an 18-pin instead of a 24, but i wasn't sure if it was safe (I've heard stories of things catching on fire thanks to power supply adapters). but since you say it works fine for you, ill take a look again.

also, what exactly is causing the GPU to not work? some motherboard-psu connection that is required for power delivery, and since the rm750 isn't connected to the mobo, it isn't getting enough power to properly run the card (just enough to turn on the lights and fan)?

or could it be that because the bios is legacy and not uefi, the 1080 ti isn't compatible? i don't want to buy something only to figure out that the problem is related to something else entirely.
 

TommyTwoTone66

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edit: i figured it out, thanks for your help

i looked at that when i realized the HP mobo took an 18-pin instead of a 24, but i wasn't sure if it was safe (I've heard stories of things catching on fire thanks to power supply adapters). but since you say it works fine for you, ill take a look again.

also, what exactly is causing the GPU to not work? some motherboard-psu connection that is required for power delivery, and since the rm750 isn't connected to the mobo, it isn't getting enough power to properly run the card (just enough to turn on the lights and fan)?

or could it be that because the bios is legacy and not uefi, the 1080 ti isn't compatible? i don't want to buy something only to figure out that the problem is related to something else entirely.
Yeah I’m not sure that will solve the issue tbh since you have a dedicated PSU just for the GPU. It should be getting all the power it needs. Worth a try though.

the 1080 works just fine without UEFI Bios.
 
Dec 7, 2021
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Yeah I’m not sure that will solve the issue tbh since you have a dedicated PSU just for the GPU. It should be getting all the power it needs. Worth a try though.

the 1080 works just fine without UEFI Bios.
if i understand correctly, it wasn't working because the corsair psu wasn't connected to the motherboard (and by extension, the power button which triggers the start sequence), and not getting the signal to turn on. the PCIe bus was giving the card just enough power to have the lights and fan come on, but not enough for the actual GPU to run, which is why i was getting an error code (and why device manager wasn't seeing it): the gpu wasn't even running. I stuck the 1080 Ti in my dad's brand-new system* and it ran perfectly fine, so i know the card works. im now waiting on the adapter to show up and hopefully it will solve the problem and i can finally get more than 40fps on minimum graphics in war thunder lol

*(5900x, crosshair vii hero, 32gb 2x16gb 3200mhz ram, 500gb wd sn750)
 

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