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CIA Apr 24, 2013 04:40 PM
Max Power use for 2008 MacPro
Have a 3.2GHz 8 core MacPro 2008, 16GB Ram, with a 5870 in it, also have the original 8800GT with a Molex to 6 pin adaptor. If I run both cards, 4 hard drives, a PCIe eSATA card, and two superdrives, will it fry the PSU? (Assuming everything, CPU, both GPU, etc is running at 100%?) I can split the power off the Optical bay and snake it down into the PCI area to power the older 8800.
reader50 Apr 24, 2013 07:26 PM
Man, the CIA is supposed to know everything. I was reading the post, it was looking good - does look like a maxed out config. But you left out the amp reading.

You can assume 80-90% efficiency for a modern power supply. And the specs say 318 W (MacTracker) which is an output spec. So max input draw will be just under 400W.

Give us a reading. What's that puppy drawing?
P Apr 25, 2013 03:28 AM
Well, the PSU shouldn't fry - generally they just make the entire computer start behaving weirdly when loaded, because it can no longer maintain power on the 12V rail. I wouldn't trust a reading at the wal either, unless you can somehow guarantee that you're loading both CPU and GPU to the max when testing - something that is harder than you think. Check the power supply rating of your Mac, and then type "power supply calculator" into google and pick one - I like this one. Enter your gear and see what it says, then compare to what your PSU says.

If you're going to really do this right and be certain, you have to calculate the load on each rail (=at each voltage). The problem is that most power-hungry things these days use the 12V rail, so that's the one you need to worry about. If you can find the rating on the 12V rail (there is often more than one, and the ratings are often printed on the PSU case), you can start adding up the amps for the power-hungry things like GPUs and CPUs to see how close to the ceiling you get on just that.
cgc Apr 25, 2013 07:35 AM
Don't all MacPros have a 1KW PSU? I know my model does (1,1 2006). 1KW is plenty for your use but run a calculator as suggested to make sure.
Waragainstsleep Apr 25, 2013 03:42 PM
Google says the PSU from the 2008 Mac Pro is rated at 980W.

If you allowed 100W for the four drives and 250W each for the GPUs (all overestimates), that still leaves you nearly 500W for the CPUs, the rest of the logic board and the eSATA card. Sounds like plenty to me.
bowwowman Apr 27, 2013 10:32 AM
Not being sarcastic, but do you REALLY believe that you are the only person out there that has loaded up & maxed out their machines........

And these machines have been out for how long now ?

What about all those graphic designers and music producers and scientists that use at least as many, and probably more, devices than you are........if a large number of their psu's were frying out under those loads, we would have heard about it by now :)

Seriously, just stop worrying, be happy & move on with your life :eek: :rolleyes: :D
reader50 Apr 27, 2013 07:08 PM
My MacTracker spec of 318W must have been typical usage. According to Apple's spec page for the 2008 MacPro, it has a maximum draw of 1200 VA. That strongly suggests a 1000W power supply.

It's designed for 4 HDs, 2 opticals, and at least one high-powered GPU + 3 regular cards. Plus a healthy safety margin. I'd say you're fine with whatever you want to throw in.
Waragainstsleep Apr 27, 2013 07:24 PM
Yeah, just give it a go and don't sweat it. People take a lot of issues with Apple for a variety of reasons but those Mac Pros are seriously well built in every respect.
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