Solution for adapter missing -12VDC with newer ATX power supplies?
Solution for adapter missing -12VDC with newer ATX power supplies?
I own an older ASRock X99 Taichi and I’m planning to upgrade its graphics card to a RTX 5070. At first it worked properly until the original power supply stopped functioning. I replaced it with a Corsair RM1000x, which now causes a Dr Debug error 19. Using an older RTX 1070 with a 650 watt PSU works fine, but it fails with the 5070. Corsair explained that the X99 needs -12V on pin 15 of the ATX power connector. They initially offered an adapter cable with a buck converter to supply the required voltage, but now claim they don’t have any and aren’t sure when they’ll get one. I’ve looked online but haven’t found any adapters except for outdated links from sites like MODDIY that used to carry them. Anyone know where to find such an adapter? I usually build my own, but after eight failed surgeries I’m stuck in bed and my PC is all I can do while gaming. Any suggestions would be really appreciated.
Welcome to the forums, newcomer!
At first things seemed okay until the original 630watt power supply stopped working.
Could you tell me the make, model, and age of the device?
Using an old RTX1070 with a 650 watt PSU works just fine.
What are the details of this unit?
Pin 15 is ground, while pin 14 is -12v.
From what I understand, you’ll need to upgrade your platform to get the best value from your purchases, whether it's for the RM1000x or the RTX5070.
From 2022 onward, 12V became optional in ATX 3.x power supplies, though only Corsair appears to have removed it, rendering their PSUs incompatible with even the 2025 Asrock boards that use it for onboard audio. You may switch to a different brand PSU or opt for an ATX 2.53 model from 2021 where Corsair would still fit. The RTX 5070 typically includes a 2x 8-pin adapter in the box. ATX 3.0 requires a 12VHPWR for the RTX 4000 series, while ATX 3.1 uses 12V-2x6 for the RTX 5000 series; if you prefer not to use an adapter, consider another ATX 3.1 PSU with a -12v rail.
Unfortunately, the options didn’t match what I could afford. My RTX5070 and RM1000x were beyond my budget after eight failed back surgeries and most of the time I’m bedridden. The only thing keeping me going is my computer, which needs graphics cards better than my 1070. The rest of the system was a gift from my son-in-law, and the Corsair HX620w worked for a while before failing under pressure. My CS650M won’t even attempt to run. I think the inrush current is too high for it.
Corsair claims just a -12v would suffice, and they said they’d send an adapter cable with a buck inverter that could work. They told me they don’t have any adapters left and aren’t sure when or if more will arrive.
Thank you for the very helpful reply! I had no idea Corsair was the only choice. I’ve had bad experiences with MSI (DOA), so I went for Corsair thinking it would be better quality. But missing the -12v is a big issue. Anyway, I quickly switched to another supply after confirming it has the -12v and also got ATX 3.1 for my 5070. Another detail I didn’t know. Goodbye adapter! I’ll be contacting Corsair for a refund.
Thanks again!
I doubt Corsair disclosed the current requirements for your motherboard on the -12V rail or the capabilities of their legendary buck converter. Probably not.
Converters from +12V to -12V are available, but understanding the current draw of your X99 from that rail is essential.
The NZXT C1200 Gold PSU specifications indicate the -12V rail can deliver up to 0.3A (300mA). This suggests your X99 should comfortably operate with less than 300mA on that rail.
There are inexpensive converter modules on AliExpress for around US $0.87, capable of handling +12V to -12V at 200 to 500mA. I’d favor sourcing a local adapter if possible.
Setting up such a conversion would require some soldering skills and tools; mistakes could be costly, though the voltages stay well within safe limits.
If you can’t obtain a refund on the Corsair RM1000X and have a nearby repair shop, they might create an adapter for your X99 to supply -12V.
@BFG-9000
Thanks for the information about the absence of -12V support in the Corsair RM1000x. I’m considering it for my RTX 4070 and will verify the motherboard specs first.
It's the somewhat gloomy part. I have everything ready—crimpers, tools, gear—to tackle this. But my back still won’t cooperate. At least not right now.
I believe a different brand of ATX PSU would actually be more affordable. 🤷♂️
Interesting points. I also own a Taichi X99 and 5070. Previously, I swapped an old RM850 for the RM850x shift. I didn't notice there were no -12V options or that the shift used smaller connectors (MicroFit). The 12VHPWR cable was set for 600W, but the PSU box had a label indicating 300W or less for PCIe! I don't recall any POST problems, except when using the RS232 COM port. The RS232 on the Taichi requires the -12V supply. I ended up purchasing an inexpensive 12V to 12V isolated DC converter and connected 12V via a 4-Pin molex connector, outputting to a 24-Pin ATX connector. It's only rated for 2W, but it's functioning properly. I believe a couple of Op-Amps also use the -12V supply.