Question PSU for GTX 970 / Ryzen 7 ?

Pimpom

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I'm building a budget APU system based on a Ryzen 7 5700G and have ordered everything except the PSU. I thought I'd use a 450W PSU from the budget line of known brands and upgrade it later if I ever get around to installing a power hungry graphics card. I was considering models like the CV450, XPG Pylon 450, Cooler Master MWE 450, Antec VP450P+, DeepCool PF450, etc.

Then I made a deal for a used GTX 970 for a good price and am wondering if 450W is enough. Old reviews indicate that the total wall power draw of a GTX 970 system with contemporary i5/i7 CPUs tops out at around 300W - roughly 250W output from the PSU. Based on those figures, it would seem that a decent 450W PSU (not high-end though) should be good enough. On the other hand, I know that working out PSU requirements is a tricky business that involves factors that are not immediately obvious from simple arithmetic calculations.

FWIW one of my old desktops uses a CX430 to power a Phenom II x4 970 with a GTS 450. Your advice please?
 

DSzymborski

Titan
Moderator
The fundamental issue is that while a 450W PSU would be enough, this isn't a particularly good group of 450W PSUs, mostly below what I would call decent when using a GPU that requires supplementary power. The CV 450 and DeepCool PF450 are both double-forward, group-regulated and the Antec VPs are in a similar boat but with even worse capacitors in most cases. Leave the PSUs designed for Pentium III platforms back in 1998 if you have an actual GPU.

The only ones on that list that I'd describe as halfway decent are the MWE if it's not the 80 Plus White and it's at least the Bronze and not the 230V only, and the XPG Pylon, which at least isn't group-regulated.

Generally speaking, these 450W PSUs were (mostly) of the quality that you can live with on an entry-level PC that doesn't have a GPU. But once you not only have a discrete GPU, but one in which you require supplementary power (so, not a 1050 Ti or 1650), then you're in a whole different world of what should be used.

Now, the cheapest you should go are PSUs in this range:

PCPartPicker Part List

Power Supply: EVGA G5 650 W 80+ Gold Certified Fully Modular ATX Power Supply ($59.99 @ Amazon)
Total: $59.99
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2022-08-07 03:03 EDT-0400


PCPartPicker Part List

Power Supply: NZXT C550 550 W 80+ Bronze Certified Semi-modular ATX Power Supply ($59.99 @ B&H)
Total: $59.99
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2022-08-07 03:04 EDT-0400


PCPartPicker Part List

Power Supply: Super Flower Leadex III Super Pro 650 W 80+ Bronze Certified Fully Modular ATX Power Supply ($59.99 @ Newegg Sellers)
Total: $59.99
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2022-08-07 03:05 EDT-0400


PCPartPicker Part List

Power Supply: Super Flower Leadex III Super Pro 650 W 80+ Bronze Certified Fully Modular ATX Power Supply ($59.99 @ Newegg Sellers)
Total: $59.99
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2022-08-07 03:05 EDT-0400


PCPartPicker Part List

Power Supply: EVGA 210-GQ-0650-V1 650 W 80+ Gold Certified Semi-modular ATX Power Supply ($64.98 @ Amazon)
Total: $64.98
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2022-08-07 03:05 EDT-0400


Now, these aren't suitable for high-end 30-series GPUs or anything, but this is the realm of quality budget PSUs, not like the 450W entry-level ones.

450W is generally not a range you want to be shopping in with quality parts, even if they only need a 450W PSU. Some of the fixed costs of manufacturers mean that it's frequently not worthwhile to make quality 450W PSUs because things like shipping, advertising, management still cost as much. Generally, the only high-end 450W PSUs you can find at all are small form factor ones, which cost a pretty premium as a result.
 
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Pimpom

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Thanks. I'll check out those recommendations for price, reviews and availability in my country (I'm not in the US). The Seasonic S12II 520 is tempting but it means a x2 jump in budget for the PSU and I'd rather pay less if some cheaper models are good enough.

In the meantime, is there something wrong with the 230V version of CM MWE other than the input voltage requirement? I live in a 230V region.
 

Pimpom

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Oh, and one more question: Is it safe to assume that a PSU will be of the same quality as another model of a different power rating in the same series? For example, if there's an in-depth review of the 750W model from series X by brand Y, will it apply to a 500W model from the same series?
 

DSzymborski

Titan
Moderator
Thanks. I'll check out those recommendations for price, reviews and availability in my country (I'm not in the US). The Seasonic S12II 520 is tempting but it means a x2 jump in budget for the PSU and I'd rather pay less if some cheaper models are good enough.

In the meantime, is there something wrong with the 230V version of CM MWE other than the input voltage requirement? I live in a 230V region.
It uses lower-quality parts. It's a definite pass. the S12 II isn't good, either; it's another ancient, group-regulated PSU. Another fine, very basic PSU, but you can no longer use that.

The problem here is that you're not looking at all in the right segment of the market. Once you went from an iGPU build to a build with a relatively modern GPU that requires supplementary power, you drastically changed your wattage/safety requirements. The XPG is the only one you've listed that I'd use in a pinch in this situation, but I wouldn't be happy about it. PSUs from the cheapest tier that can even be called PSUs are now inappropriate for your rig.
 
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Pimpom

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Noted.
Out of the PSU models you listed, only the NZXT C550 seems to be available in my country. At the equivalent of US$56 shipped, it seems to be a good solution. There's also the Corsair CX550M for $52.

I live in a remote corner of a developing country. I've been designing and building electronics circuits - from simple stuff to quite complex ones - from the component level for 50+ years and understand most of the technical aspects. The problem is in finding the relevant bits of information about a product. I don't know how you guys do it.

A plethora of online computer shops have sprung up in recent years, probably triggered by COVID lockdowns. The problem is with their listing and search engines which often miss products they have in stock.
 

DSzymborski

Titan
Moderator
Noted.
Out of the PSU models you listed, only the NZXT C550 seems to be available in my country. At the equivalent of US$56 shipped, it seems to be a good solution. There's also the Corsair CX550M for $52.

I live in a remote corner of a developing country. I've been designing and building electronics circuits - from simple stuff to quite complex ones - from the component level for 50+ years and understand most of the technical aspects. The problem is in finding the relevant bits of information about a product. I don't know how you guys do it.

A plethora of online computer shops have sprung up in recent years, probably triggered by COVID lockdowns. The problem is with their listing and search engines which often miss products they have in stock.
I'm glad the NZXT and CX are available there. There's certainly no need to explain the topologies then! Being in a developing country makes PSUs trickier because there's even more of a reason to worry about issues like ripple and possible inconsistent input voltage. I'd obviously like you to have to pay as little as possible, but I want you to have the safest PC that's practical.

Generally speaking, the hobbyist community does a good job tearing down PSUs for reviews or just in simple forums and even on Reddit. A lot of the design for these consumer-level PSUs comes from the era in which the rudimentary GPUs didn't use as much power today and CPUs required the +5V rail. That changed after the Pentium III as ATX spec changed, resulting in +12V PSUs and eventually the removal of the 240W limit for the +12V rails. With the vast majority of PCs these days, especially gaming ones, requiring +12V power, those old group-regulated ones end up having really nasty crossloads that frequently put those old ones way out of spec. The standard for quality PSUs these days, as you might guess, are DC-DC designs using buck converters.

My expertise here is highly specialized. I can operate and interpret a load tester/oscilloscope and disassemble and understand a PSU's parts, but I was a math/econ major back in college (and weirdly ended up a journalist/data consultant, though the latter is less weird), and could definitely not design a circuit!
 

Pimpom

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Thanks for your time and expertise.

I was a maths major in college too but I dropped out due to poor health. I was one of 22 students selected by the central (federal) government for advanced studies while doing the normal college course. A bunch of us used an IBM 1620 to work out the basics of Armstrong & Co's trip to the moon in 1969. At the same time, my growing interest in electronics, with access to just a few hopelessly outdated books, took up a lot of my time and focus. And my region was ravaged by insurgents calling themselves patriots (they nearly succeeded in kidnapping me). It was all too much and my health gave out. I dropped out of college and took up teaching myself electronics in earnest.

Okay okay, that's enough of an old fart reminiscing about the past. Thanks again.
 

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