Hmm... it isn't obvious how "drawing too much power" would endanger your drives before the power supply gives in. Per EveryMac.com this Mac Pro can support up to 300 W total in the PCI bus. But the 200 W for your card seems to apply only for heavy duty GPU running, like BitCoin mining and it draws much less even when gaming. Unless your PCI is already filled up with other stuff, based on the numbers the bus should be able to power the card by itself.

I'd be suspicious whether the card somehow puts the extra power you provide to it back onto the bus, thereby putting overvoltage on some sensitive items like your HDs. Is the extra power you provide 12 V or 5 V?

I have two MacPro's of the same vintge. Merrily humming along with 2 HDs in each of them & my swapping out disks regularly to try things out. Has yet to kill a disk. I would be highly suspicious of the card. Unless it runs without the extra power I'd toss it.

Just my $0.02,

Uli

On 1/7/19 8:02 PM, Ken Cunningham wrote:
This has nothing to do with Macports, but  there are many people here who know 
stuff about this...

About six months ago I put a new Metal-capable Sapphire HD 7950 video card in my 2010 
MacPro (8 processors) to run Mojave. It required two extra power cables to give it 
all the extra juice it needs, in addition to the usual bus power. It seems to pull up 
to nearly 200W according to Tom's hardware 
<https://www.tomshardware.com/reviews/radeon-hd-7950-review-benchmark,3207-9.html>.

Since then, I have bricked three SATA hard drives on that MacPro, two older 2TB 
ones (2012 era) but one 2016 4TB SSHD that was pretty new.

All three of the drives just disappeared off the desktop unexpectedly with a 
message about not powering them off properly, and then at reboot would not spin 
up, and never did work again.

I'm suspicious that the 7950 is pulling too much power and causing the SATA 
hard drives to fail. I also have an AJA Kona 3G in that machine that pulls 20W.

Anyone seen this?

Ken

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