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Planning on building a computer but need some advice? This is the place to ask!

Planning on building a computer but need some advice? This is the place to ask! /c/buildapc is a community-driven place dedicated to custom PC assembly. Anyone is welcome to seek the input of our helpful community as they piece together their desktop.

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Will I need a new PSU for a GPU upgrade? (beehaw.org)

submitted 8 months ago* (last edited 8 months ago) by [email protected] to c/[email protected]

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So currently I’m running a 5800x and a regular 2060. I’ve got a 650w gold PSU that’s about 4 years old, no problems with it at all. I’m thinking about upgrading to a RX 7800 XT because GeForce prices are perpetually absurd. It seems like it would be enough power, but the few things I’ve read say that I need at least a 750w if I go with the AMD (because they’re power hungry?), but 650w would be fine for a 4070ti. If I have to buy a new PSU, I feel like it would wipe out any savings I might get by buying AMD over Nvidia. How can I definitively know if I need more power?

Full disclosure, I understand the concept of undervolting, but I’m not nearly confident enough to mess with the settings.

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[–] [email protected] 3 points 8 months ago* (last edited 8 months ago)

The 7800XT (263W) has over 100W higher TDP than the 2060 (160W). It ultimately comes down to what other components you have, but you will be pushing the ceiling on a 650W PSU with the 5800X (105W).

You are under the limit based on TDP, but during peak loads, may not have enough overhead to not reduce the life of your components. That said, if you have fewer than 4 DIMMs of RAM, and only M.2 SSD storage, you are probably fine.

Let’s round up and say 75W for Mobo, 32W for RAM, 10W for storage, and 5W for LEDs, you come out right at 500W. Add 20% for thermal overhead, and you’ve got 600W. Very close, but should barely be stable.

This assumes a reference GPU. An OC edition could easily blow this calculation, but do your own math.

Definitively, buy a kill-o-watt, fire up a CPU+GPU stress test, and measure power draw at the wall. Add 100-200W to account for the new card, and see if it exceeds 650W.