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PC Power Supply Discussion Troubleshooting and discussion of computer power supplies

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Old 4 Weeks Ago
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We measured 339.72W peak during the Metro benchmark with a Vega 64. Our equipment is able to catch power spikes down to 2ms.

Tom's measured 385W with scopes, but personally I don't trust power clamps & scope combos for those measurements, because of EMI noise messing with the signal. Also there is a problem with scopes, not being able to sync Amps and Volt data, so Watts can be highly inaccurate.
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Then it may be the video card that should have larger buffer capacitors to cut down the peak power demands; let's play with some numbers for energies:


Suppose 5 x 1000uF buffer capacitors at 12V, which have 0.36 J in all (of which only a fraction is available)

385W for 2ms is 0.77 J

Last edited by ashiekh; 4 Weeks Ago at 05:06 PM.
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Quote:
Originally Posted by jonnyGURU View Post
If the spike was longer than 4ms (I'm seeing between 2 and 4ms), then the XFX would shut down as well.
What role does the duration of the spike play in triggering OPP? I know I've brought up similar questions on this forum perhaps a year ago pertaining to whether the protections trigger based on instantaneous power or average power over some defined finite interval of time.
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Quote:
Originally Posted by jonnyGURU View Post
EDIT: Yeah... your card has a HELL of an overclock from the factory. You're actually exceeding 85A on the +12V rail and the PSU's OPP is shutting it down.
That doesn't sound right.
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Modern day Seasonic PSUs have a lower OPP trip point than a lot of other PSUs. That's why your XFX works. If the spike was longer than 4ms (I'm seeing between 2 and 4ms), then the XFX would shut down as well.
If seen people using 550W and 650W PSU's with that graphics card without a problem, even Seasonic's. The only problems were defective power supplies that didn't like the transient loads, but those could be fixed by an RMA.
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Quote:
Originally Posted by jonnyGURU View Post
Yeah... your card has a HELL of an overclock from the factory. You're actually exceeding 85A on the +12V rail and the PSU's OPP is shutting it down.
I'm way out of my depth here, but can one card use more than 1kW? and if so, how does one keep it cool? or are we just talking a 2ms transient?
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Quote:
Originally Posted by ashiekh View Post
I'm way out of my depth here, but can one card use more than 1kW? and if so, how does one keep it cool? or are we just talking a 2ms transient?
Jon's speaking on quick (2-4ms) power spikes that happen in dynamic load changes.

That's not an uncommon event for any component, in the past many HDDs starting up at once caused similar problems on PSUs
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What sort of values does a high power video card have for the buffering capacitors? All my technology is about 10 years old, so I don't have access to such equipment.
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Quote:
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What sort of values does a high power video card have for the buffering capacitors? All my technology is about 10 years old, so I don't have access to such equipment.
All over the place to be honest. Varies by board vendor, reference design, etc.

That kind of info is hard to come by as well unless you have a specific card on hand as most reviewers don't do PCB breakdowns. A major annoyance on all fronts with DRAM, GPU, & Motherboards especially.
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And here was I thinking I was the only major annoyance...
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Quote:
Originally Posted by -The_Mask- View Post
That doesn't sound right.


If seen people using 550W and 650W PSU's with that graphics card without a problem, even Seasonic's. The only problems were defective power supplies that didn't like the transient loads, but those could be fixed by an RMA.
Vega 64's?

I don't see using even a single Vega 64 at stock speeds on a 550W. Unless they bought it to just do cryptocurrency (no spikes).

We don't see this issue with ANY OTHER graphics card. Vega 64 is the only card that "brings out the worst".
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