I'm upgrading an eight-year-old desktop and want to know whether my NZXT C650 power supply is suitable for the new components: a Ryzen 7 7800X3D, Sapphire RX 9070 XT, MSI Pro B850-P motherboard, 2×8GB of 6000MHz RAM, one M.2 SSD, and one hard drive. Power calculators estimate roughly 525–575W, although one appears to include an additional 100W for USB power delivery that my motherboard may not actually use. Since those estimates are fairly close to the PSU's 650W rating, should I keep the current unit or replace it?
2 Answers
The calculators are estimating sustained consumption, which is why their results differ slightly. The extra USB power figure probably isn’t a meaningful load for this motherboard. The bigger concern is brief power spikes from the RX 9070 XT, especially with an eight-year-old PSU whose components may have aged. Even if the system runs near the calculated wattage, the available headroom is fairly limited, so replacing it with a quality 750W-or-higher unit would be the safer choice.
I’d upgrade to a 750W PSU rather than run the new build on the old 650W model. That gives the graphics card more room for transient spikes and avoids relying on an aging power supply.
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