slight power consumption concern

EquineHero · Jan 17, 2018

I've got a Xeon X3450, a Quadro 4000 (GF100), 4 ECC DDR3 DIMMs, and one 7200RPM disk all powered by a 250W power supply.

If the math is done correctly:

Xeon - 95W

Quadro - 140W

RAM - 4W

Drive - 6W

Assuming everything is consuming max power, that's only 245 watts, leaving 5W for USB stuff like mouse and keyboard.

It's a Dell HIPRO power supply, and HIPRO makes some of the most reliable power supplies in the world.

Not to mention it's a server power supply.

Given all things considered, I should be fine with 245W at 100% load, right? They don't make any bigger PSUs for this model and I'd hate to have to buy a different one (the ATX 24 pinout is slightly different, +12v in two places wehre there's no pin and +3.3v instead).

Is my concern valid, or should I not be sweating this?

For reference, it's an old PowerEdge R210 1U rack server.

mrmez · Jan 17, 2018

All depends on how hard you push it.
For a gaming/server/video applications I'd say hell no.
For office stuff, it's fine.

Possible problems:
Pushing your psu to the max will shorted it's life, and possibly cause crashes when it can't deliver enough power.

Solandri · Jan 17, 2018

A CPU and GPU's TDP isn't the component's power consumption. It's the recommended minimum amount of cooling. i.e. The power consumption is guaranteed to be below the TDP. How much below varies considerably. A 95W TDP CPU could draw 95 Watts. Or it could draw a little more than the next lower TDP. Since the next lower level TDP is 65W, the CPU might only draw 68 Watts max. The only way to know for sure is to find reviews which tested that exact CPU or GPU with equipment to precisely measure power consumption.

That said,

1) You want a minimum of about 40 Watts of headroom between your system's max steady state power consumption. HDDs only draw about 3-9 Watts, but they can draw up to 45 Watts for a few seconds while they're spinning up. If your system is chugging along at 245 Watts and the HDD goes to sleep dropping it to 239 Watts, when the HDD tries to spin up again it could temporarily push the system up past 280 Watts.

2) You really want to keep steady state power consumption at or below about 80% of the PSU's rating. If it's a cheap power supply (i.e. not rated bronze, silver, gold), you probably don't want to go much past 60%. The PSU's power rating should be thought of as more like the PSU's max sprinting ability, not its distance running ability. (Likewise, you don't want to get too big a power supply. Peak efficiency is usually around 70%-80%, so if you get too big a power supply you're just wasting electricity.)

Edit: And you left out the power consumption of the motherboard (usually about 10-15 Watts). I'd recommend finding a different case to put all this in, along with a bigger PSU. But if you really want to do this, see if you can use something like a PicoPSU to power the GPU. Those draw power from an external AC adapter brick. The drawback is that its 12V / 5V rails may deviate from the PSU's 12V / 5V rails feeding the other components, which can cause stray eddy currents. This can lead to random and unpredictable symptoms.

EquineHero · Jan 18, 2018

mrmez :

I've been gaming on it for the last 4 hours with the Quadro overclocked, haven't noticed anything out of the ordinary. PSU fan doesn't ramp up under load and stays relatively cool. The CPU is always under 65C with a single fan on the Cooler Master d92 I have zip tied to it. The thermal capacity of the d92 is 250W guaranteed under 100C.

Solandri :

The motherboard is some weird ATX with the RAM below the CPU, and the PCI above (more like BTX). However BTX cases usually have the panel open away from the user when the PC is on the right side, and BTX cases also have the GPU fan-up. If I were to mount this board BTX style, the panel would be open towards the user and the GPU would be fan-down.

I would need a custom case for it. The 6-pin connector is actually soldered to the PSU, I opened it and replaced a SATA drive connector with the 6-pin. PSU didn't come with one.

I've disabled HDD LSPM. It's also not a "cheap" power supply at about $200 for a replacement. I think all of HIPRO's PSUs are at least Silver.

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