[SOLVED] Can I use my existing PSU for new AMD R9 5900 build?

stravencroft

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My current build

Right now I"m using a Seasonic Prime Gold 850W (not the focus variant) for my system along with a EVGA XC3 Ultra Gaming RT 3080 I plan on also migrating. I was curious if I would be able to this PSU with my next planned build which would be a 5x series likely a 5900 on a Asus Rog Crosshair VIII hero board. Putting that in pc part picker detects no issues but running that through a voltage calculator on seasonic's website seems to encourage me to purchase at least a 1000 watt PSU. I'm also running 5 fans, 2 SSD NVME , 1 SSD Sata, and 2 7200 RPM sata drives.

Though to be fair scanning my 3080 GPU with EVGA's X Precision tool on my current i7 7700k setup also seemingly encourages me to purchase a 1020 plus psu though it keeps detecting my card as 2 GPUS rather than 1.

In any event should I be good with my existing 850w PSU on a 5x series AMD build? Or should I be looking at a 1000/1300 upgrade. Nothing cheap about those PSU's.
 

Darkbreeze

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3900x uses SIGNIFICANTLY more power, by design, than the Ryzen 5900. 65w versus 105w with the stock configuration. Not comparable at all in terms of power consumption. Now, the 5900x is a 105w part like the 3900x, so it really matters exactly what part you are talking about but even so, none of these parts would require you to increase the power supply beyond what you already have if you are not already having problems. Especially when the 7700k uses as much as 185w under a full load at the stock configuration. The "91w" listing for that CPU is ONLY accurate for the base clock frequency at a full load. It is not accurate for the all core boost frequency at the stock boost profile, and Intel has always been misleading with their thermal design power specifications in this way.

You would have no problem, and would in fact be using less power, by moving to the 5900x. AMD rates the TDP for their processors at full boost frequency.
 
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Darkbreeze

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I don't see any reason you would need to change power supplies if it's working fine with that RTX 3080 right now. The changed platform isn't going to create any great increase in power consumption (In fact, it will probably use LESS power), UNLESS you are planning to try overclocking the CPU or graphics card. Then, you might want to look at 1000w or higher units, but even then, you might not need to.
 

stravencroft

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That might be why the EVGA program it's subtly encouraging me to upgrade now. I haven't tried OCing the GPU yet. Although with the new NH-D15S cooler I have OC'd my i7 7700k for the first time. I'd like to have the option to OC the 5900 when it's time to upgrade. I'm just not sure if the 850w PSU could still get the job done.

I don't ever see myself overclocking the 3080 for any reason however... the thing scares me it gets so hot even with the improved airflow changes I"ve made to assist.

Anyone else running a similar PSU wattage for their AMD 3900x/5900 builds?
 

Darkbreeze

Retired Mod
3900x uses SIGNIFICANTLY more power, by design, than the Ryzen 5900. 65w versus 105w with the stock configuration. Not comparable at all in terms of power consumption. Now, the 5900x is a 105w part like the 3900x, so it really matters exactly what part you are talking about but even so, none of these parts would require you to increase the power supply beyond what you already have if you are not already having problems. Especially when the 7700k uses as much as 185w under a full load at the stock configuration. The "91w" listing for that CPU is ONLY accurate for the base clock frequency at a full load. It is not accurate for the all core boost frequency at the stock boost profile, and Intel has always been misleading with their thermal design power specifications in this way.

You would have no problem, and would in fact be using less power, by moving to the 5900x. AMD rates the TDP for their processors at full boost frequency.
 
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stravencroft

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Many thanks! It's good to know there's finally a part I don't need to purchase to make the leap to my next build!

It is worth stating that while I've successfully overclocked the i7 7700k once(for the first time last night since I've owned it in the past 2.5 years), I have also stress tested the 3800 two or some times but never ran it Overlocked with any game or application beyond the precision tool . Further, I tested the 3800 before I overclocked the 7700k. I've never overclocked both at once. No idea if I have enough power for that. If I did I'd be more than fine with 5x AMD build though it sounds like.

Worst that could happen is it'd just crash right? No actual damage I hope.
 

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