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Old Dec 17, 2012, 06:22 AM   #51
slughead
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Quote:
Originally Posted by macz1 View Post
Yes. the three pins o the sata connector are shorted together anyway as soon as they go into the 18 AWG cable. The 4.5A limit concerns only the SATA connector itself. Earlier Mac Pros had also a 4-pin Molex connector for the peripherals which is even rated for 11 amps.
As far as I know, such a peripheral power connection is allowed to draw 110W in total (6.5A per pin) according to ATX specifications. The last AGP graphics cards used those molex connectors as auxiliary power source and had already TDPs well above 50W... It's perfectly safe to draw 5A from it.
I agree: Older Mac Pros have 4 pin Molex which is probably fine. However, you specifically said that the SATA power connector was rated for 5 amps which is not only wrong, but misleading (it's only rated for 1.5 amps / pin and it has three 12v pins). I'm not sure when they made the transition but newer MP owners should definitely think twice before using the SATA plugs to power their cards.

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Originally Posted by macz1 View Post
An additional PSU is the safest solution of course, but why add another 400W to the vastly underutilized 900W+ the internal PSU of a Mac Pro can deliver? It's almost painful to think about from an engineering point of veiw...

You're right, it is painful and ridiculous. That's the way Apple made it though.

Though I'm fairly sure 250watts (7970's peak power requirement) is probably fine on the Mac Pro's tracers, people should always be wary of anything with an 8 pin. MacVidCards is right: the 8 pin connector gives the 7970 the potential to destroy your MP.

As far as drawing from the 5.25" bay, that doesn't solve any problem, and for new (post-2008 ??) MP owners, it creates a new problem.

You still haven't addressed the issue of making sure current is limited to 37.5 watts / lead through the mobo tracers (which is what we're presuming it's rated for). You just kind of assumed drawing power from the PCIe bay will solve that problem.

Last edited by slughead; Dec 17, 2012 at 06:28 AM.
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Old Dec 17, 2012, 07:49 AM   #52
All Taken
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MacVidCards is right: the 8 pin connector gives the 7970 the potential to destroy your MP.
Any card above the power draw of a 5870 has the potential to destroy your Mac Pro, if we were to dumb it down to simplest of stats it's anything above what Apple supports and that's a 5870. MacVidCards himself sells more powerful cards than the Mac Pro 'typically' caters for. That in itself is pushing the edge of unknown. Macvidcards can and does say that the PCIe is giving bla bla bla amounts of power and that the 2 6 pin are giving bla bla bla but in actual fact anything other than a 5870 is pushing that limit.

We can all make educated guesses as to the safe limit until the cows come home but where are we? 4 pages of dialogue and nobody is any closer than postulating theoretical limits and safety of card X in the Mac Pro.

Anyone willing to donate toward the cost of a back pane board for a 2010 Mac Pro? I'll soon let you know the result in one post.
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Old Dec 17, 2012, 09:26 AM   #53
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Anyone willing to donate toward the cost of a back pane board for a 2010 Mac Pro? I'll soon let you know the result in one post.
You should donate it yourself to prove all of the nannies wrong.
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Old Dec 17, 2012, 10:16 AM   #54
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You should donate it yourself to prove all of the nannies wrong.
Ha Ha I sure should right?. Hey who said you were wrong? Maybe the limit is right? Maybe it's much higher - past the squabbling I think it's better all round and the answer worth more than '+1 to us, we were right'. I'm not 600 desperate for an answer but in monetary terms i'm maybe 200 interested in one. Lots of users are interested in this and it's better than the 'Nannies' claiming XYZ is safe when actually it's a guess. Also better than people claiming XYZ card works when perhaps in reality the traces can't take the load.

I have a question, genuine question that could be answered in a non passive aggressive fashion.

MacVidCards - You work with Mac cards and sell them as a business model. Have you never thought of actually testing this? The credit to your name alone would greatly help your reputation. I'm not saying you need it, but it must have crossed your mind? Think of the added sales....
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Old Dec 17, 2012, 12:33 PM   #55
ActionableMango
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Originally Posted by MacVidCards View Post
Problem solved !!!

If it works for him, it'll work for anyone.

Have at it boys !!!

And the good Dr. will be happy to cover any casualties, he is a Dr. after all.
I believe people should be able to freely report on their success or failure. It adds to our collective knowledge.
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Old Dec 17, 2012, 02:08 PM   #56
darkcoupon
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After searching and searching for any kind of official specs from Apple on PCIe slot or aux power limitations, the only Apple provided specs I can find can be seen on the tech specs page for the current model Pro:

http://www.apple.com/macpro/specs.html

Under PCIe Expansion it clearly states "300w Combined Maximum" for all four slots. No mention of aux power or single slot limitations. Now, considering the fact that the guy in Germany was mentioned to have a RAID card that probably draws around 60-75w in combination with a GTX 580 which draws a maximum of 244w, I'm convinced that combination was more likely to blame for his system failure rather than the simple assumption that he was tryin to power a card with two 8-pin power connectors.

EDIT: I'm posting from the mobile site so I appologize for not being able to hyperlink that page.
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Old Dec 17, 2012, 02:15 PM   #57
All Taken
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Originally Posted by darkcoupon View Post
After searching and searching for any kind of official specs from Apple on PCIe slot or aux power limitations, the only Apple provided specs I can find can be seen on the tech specs page for the current model Pro:

http://www.apple.com/macpro/specs.html

Under PCIe Expansion it clearly states "300w Combined Maximum" for all four slots. No mention of aux power or single slot limitations. Now, considering the fact that the guy in Germany was mentioned to have a RAID card that probably draws around 60-75w in combination with a GTX 580 which draws a maximum of 244w, I'm convinced that combination was more likely to blame for his system failure rather than the simple assumption that he was tryin to power a card with two 8-pin power connectors.

EDIT: I'm posting from the mobile site so I appologize for not being able to hyperlink that page.
We'll never know without a true test though will we? Rhetorical. With all due respect, another 2 pages of circles could be filled out and it still wouldn't lead us any closer to an answer.
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Old Dec 17, 2012, 02:31 PM   #58
darkcoupon
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We'll never know without a true test though will we? Rhetorical. With all due respect, another 2 pages of circles could be filled out and it still wouldn't lead us any closer to an answer.
Yes, but since Apple only mentions a combined power limitation in any of their literature, has it been proven that the two aux power plugs draw power from their own PSU traces as everyone seems to assume, or are they more likely piggybacked from the PCIe slots and included in this combined 300w limitation?

Last edited by darkcoupon; Dec 17, 2012 at 02:41 PM.
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Old Dec 17, 2012, 02:38 PM   #59
All Taken
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Originally Posted by darkcoupon View Post
Yes, but since Apple only mentions a combined power limitation in any of their literature, has it been proven that the two aux power plugs draw power from their own PSU traces as everyone seems to assume, or are they more likely piggybacked from the PCIe slots and included in this 300w limitation?
They're not included in the 300w limitation. Think about it, a RAID card and a 5870 + a GT120 and maybe another RAID card just for a full bay. What's the combined Wattage?
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Old Dec 17, 2012, 03:07 PM   #60
darkcoupon
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They're not included in the 300w limitation. Think about it, a RAID card and a 5870 + a GT120 and maybe another RAID card just for a full bay. What's the combined Wattage?
Assuming the RAID cards draw 60w each, that would be around 370w+...far above Apples recommended specs whether the aux plugs are included or not
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Old Dec 17, 2012, 03:21 PM   #61
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Originally Posted by darkcoupon View Post
Assuming the RAID cards draw 60w each, that would be around 370w+...far above Apples recommended specs whether the aux plugs are included or not
Here's an avenue to explore. Users of this forum have previously used a 5770/5870 and 3x GT120 to get around 10 displays working. Now they don't have problems. Assuming 2 6 pin connectors are used on a 5870 and the GT120 are all in use, what is the combined draw then?

The total draw for that setup applied to one card connected to 2x 6/8 pin would use more or less power?

Is the 300w total power spread across the PCIe slots evenly or added subtracted as required? i.e 75w + 150w from the 2x 6 pin? or up to 300w via PCIe slot and 150w from 2x 6 pin?
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Old Dec 17, 2012, 04:05 PM   #62
darkcoupon
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Originally Posted by All Taken View Post
Here's an avenue to explore. Users of this forum have previously used a 5770/5870 and 3x GT120 to get around 10 displays working. Now they don't have problems. Assuming 2 6 pin connectors are used on a 5870 and the GT120 are all in use, what is the combined draw then?

The total draw for that setup applied to one card connected to 2x 6/8 pin would use more or less power?

Is the 300w total power spread across the PCIe slots evenly or added subtracted as required? i.e 75w + 150w from the 2x 6 pin? or up to 300w via PCIe slot and 150w from 2x 6 pin?
Any links to threads on this? The GT 120 draws what, 60w? A 5770 Will draw 108, so 3x 120 and a 5770 would be right around 290w, within spec. The 5870 draws around 80w more than 5770 so it would be far over spec.
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Old Dec 17, 2012, 04:38 PM   #63
All Taken
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Originally Posted by darkcoupon View Post
Any links to threads on this? The GT 120 draws what, 60w? A 5770 Will draw 108, so 3x 120 and a 5770 would be right around 290w, within spec. The 5870 draws around 80w more than 5770 so it would be far over spec.
I can't find the 5870 and GT120 thread but i'll hopefully have it by tomorrow. In the mean time I did find an interesting article on 2 5870's and some actual power draw readings.

http://www.hardmac.com/articles/331/page1
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