A 750W PSU is generally recommended for the RX 7900 XT, but given your instability, 850W offers a safer margin.

I'm using a be quiet! Straight Power 12 M 850W with my 7900 XT paired with a 7800X3D. Works perfectly, runs quiet, and the fully modular design made cable management so much easier. Just make sure whatever you choose has enough PCIe power connectors for the card.

OMG I remember trying to jam a huge power supply into my first mini build, it was a total nightmare! I was literally sweating trying to get the side panel to close without snapping a cable lol. It's crazy how much space those cables take up if you don't get the right brand... Quick question tho, what specific case are you actually rocking right now? Limited space can mean so many things and it totally changes what I'd suggest for cable stiffness, especially since some brands use those really stiff ribbons while others are way more flexible. Some brands are known for being way more compact than others too. Tbh you should just check out that PSU tier list on the cultists site, it is seriously amazing and lists like every brand imaginable! Just Google 'PSU tier list' and you'll find the whole breakdown. I saw a fantastic video on YouTube yesterday that compared a bunch of units for the 7900 XT specifically, just search for 'best 850w psu for radeon' and it should be the first result. It goes way more in depth than we can here!

To add to the point above: the collective advice here is spot on regarding those power spikes and the need for a robust 850W modular unit! I actually went through a similar ordeal with my current setup where I completely underestimated the peak draw of my GPU during heavy loads. It was a total nightmare because I kept getting random black screens right when the action got intense! It turns out my old unit just couldnt react fast enough to the surges, even though the labels said it should work. Looking back, that DIY experience taught me some vital lessons:

• Peak load handling is just as important as the total wattage rating on the box.
• High-efficiency units are fantastic for keeping heat down in small cases.
• Modular cabling is a total lifesaver for maintaining decent airflow in tight spots. Swapping in a premium high-wattage model made the stability since then absolutely amazing! It is honestly such a relief to play without worrying about a crash. It is fantastic how much a solid power foundation changes everything when you are building a high-performance rig in a small footprint.

Can confirm this works. Did the same thing on mine and its been solid ever since.

Honestly, those random crashes are definitely a sign your current unit is struggling with those power spikes. High-end cards like the 7900 XT can pull way more than there average TDP for a split second, and a 650W unit usually cant handle that without tripping a protection circuit. You realy want something with high-quality Japanese capacitors because they handle heat better, which is SO important if your case is small and has limited airflow. I've been using the Corsair RM850x (2021) for a bit and it’s basically the gold standard for reliability. It is fully modular, which helps with your cable management, though the cables can be a little stiff. If you are really worried about space, maybe check out the Seasonic Focus GX-850. Seasonic units are known for being legendary in terms of longevity and they tend to be a bit more compact than other brands. Tbh, its better to spend the extra money now for peace of mind. Idk the exact dimensions of your case, but those two are super solid choices.

I totally agree with what was said about those power spikes. I was super nervous about my own build for the same reason, tbh I just dont want anything to catch fire lol. Quick tip: definitely look for something that is ATX 3.0 certified. They are specifically designed to handle those sudden jumps in power that the 7900 XT does without shutting down your whole system. Since you have a small case, maybe check out the MSI MPG A850G PCIE5 850W 80 Plus Gold. Its fully modular and a bit more compact than some others, which helps with the airflow. Better to have that extra headroom for peace of mind!