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Old Dec 13, 2012, 09:32 AM   #101
lixuelai
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Originally Posted by slughead View Post
You still have no idea what the "specs" actually say, in spite of the fact that several people have told you. 6 pin standard only has FIVE wires, TWO of them 12 volt leads. Yes, we can all see there is a 3rd 12 volt lead on most 6 pin cables, but this is acting OUTSIDE the standard but does NOT imply the PSU or in this case the motherboard tracers are able to provide the 150watts of power that might be drawn. In fact, I have a PSU running my GTX670 right now with only two 12v leads.

I'll do you one better: I actually looked up the physical limitation of these 6 pin wires/plugs and found out that it's somewhere around 280watts per cable!

What does this mean? Absolutely nothing! I really don't give a crap about some $15 cable I got off E-Bay or what it's rated for. What really matters is which expensive components might get damaged.

Heck, I don't even care if the PSU can't handle it. The PSU has safeguards in place. I'm most worried about the motherboard tracers, which is an Apple-specific design flaw. These thick wires are more likely to heat up and damage surrounding components than to literally explode or pop.

Your anecdote of it working without frying is not the end-all, either. I've run too much current through circuits I've built before which have run many times before failing. The problem is with component longevity. Even if it'll take a year to run into the circumstances that will kill my Mobo, that's not acceptable.

You have presented no evidence saying you have any idea what the tolerances are for these tracers, and instead you have some unfounded ideas about the way power is distributed. At least, I think they're unfounded, being as how you've given no pictures/charts/graphs/links/sources/spiritual channellings otherwise.

It's very frustrating having a conversation with someone while 1) posting links they don't read 2) being told there are sources and not being shown them.

That said, after reading a couple reviews stating the TPD to be around 250, I think you're probably right that it's safe. The review I read initially had the TPD at around 275 peak, which is really pushing it. Would I risk it in a >$2500 Mac Pro ? No, but I think it's probably okay.

As for the tone of this "debate"... I happen to agree with a lot of people here:








So now that I'm kind of on your side (no thanks to anything that you've said, by the way), can you back up ANY of the claims you made? Where's the source on the tracer map? Where is the "spec" of how much current those tracers were designed to carry?
FYI the review you read that had 275w max is likely running Furmark. Just for reference the GTX570 everyone and their grandma buys for their Mac Pro nowadays hits like 300w running Furmark. The average load of the HD7970 GHz is a bit higher than the GTX570 measured by different websites.

In fact the HD7970 non-GHZ measures less than the GTX570.

Avg Load/Peak Load/Max Load (FurMark)
GTX570 is 166/190/298
HD7970 is 163/189/270
HD7970 GHZ is 209/238/273

And some people buy OCed GTX570 for their Mac Pros...

Last edited by lixuelai; Dec 13, 2012 at 09:43 AM.
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Old Dec 13, 2012, 10:44 AM   #102
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Originally Posted by All Taken View Post
Just stop. No facts are available and you're talking like you're advising people with them. At least Slughead realises it is an area of unknown. I would genuinely like to know the true limit here instead of listening to misinformed users spouting off about a limit they know nothing about.

----------

In terms of a true test what would we need?

Back Pane logic board for a 2010 Mac pro?
A couple of cards 250w+ at load? (In order to verify results)

I won't say it will work with (X) wattage on the traces as nobody really knows, it hasn't been tested. I also won't adopt the crush and refute approach to new posts on the matter as seen across the boards. Until we know we shouldn't form the opinion that a couple of people have repeated to be fact!!

Anyone have anything constructive in terms of a test setup?
As far as a test setup I'd say '09 or '10 Pro, graphics cards that draw 250w, 275w, 300w, and 350w max TDP respectively and software that will run each card as close to it's maximum as possible, and maybe a watt meter to measure what the cards are actually drawing? Run each card for several hours from lowest maxt TDP to highest until it fries?

Still wouldn't be a great long-term evaluation and wouldn't really provide any solid reference.
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Old Dec 13, 2012, 11:13 AM   #103
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Originally Posted by All Taken View Post
I've read and asked the question myself, the 'fact' of it all is that the community doesn't know either way. Many have taken to repeating the same statement about the connectors and traces etc etc but don't have any proof. Sure we have loose specification but until somebody such as the OP tries, we don't know.
Actually, I wouldn't characterize it like this at all. We have hard-and-fast documentation about the PCIe power spec. 6-pin connectors are officially rated at 75W, period. It's in the PCIe power spec, which was linked earlier in this thread. Therefore, it's safe to conclude that the Mac Pro can safely drive a card that requires up to 225W. Beyond that, nobody knows for sure (except perhaps revelstudios?), so the general advice has been to not risk it and just use an external power supply for cards that need more than 225W.

Everyone knows that there are tolerances built into the system, and some amount of overhead over the rated 75W, but this is generally where the risk vs. reward question comes in -- do you feel confident enough that you can pull double the current through that connection on the motherboard, or not? Many people take the safer side and go with the external PSU option. Some people might even just use a converter cable and risk it. I think one of the biggest objections to the positions taken in this thread is simply the recommendation that it's totally fine and everyone should just use the converter cable. There have been many new posters on these boards asking for help with upgrading their GPU, now that it's relatively easy to just drop a standard PC card from either NVIDIA or AMD into the Mac Pro. I certainly haven't feel comfortable telling people like this that they can ignore the PCIe power spec and run a 300W card without any problems. I've never said that it might not work, but revelstudios seems to have some pretty detailed information and some of us are interested in finding out more details about it.
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Old Dec 13, 2012, 11:27 AM   #104
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Originally Posted by Concorde Rules View Post
Let's just put this 2/3 12V wire thing to bed.

Based on these sources:
http://www.pcisig.com/developers/mai...11c665ac770768
http://www.playtool.com/pages/psucon...ml#pciexpress8

The 6 pin is 3x12V and 3x Grounds.
The 8 pin is 3x12V and 5x Grounds.

The difference in current carrying capacity is APPARENTLY the rating of the 12V wires, at 2.083A and 4.167A respectively, now if Apple have used higher gauge wire from the PSU to the backplane traces then we can safely say that between the PSU and the backplane we are within specs.


The questions we need answering are:

1. The rating of the backplane traces
2. The rating of the mini 6-pin adapter on the backplane.
3. If there is any redundancy in the backplane's traces.
Some of my confusion or misunderstanding stems from the fact that I was not aware that the 6-pin connection usually has 3 12V leads. Is this a new thing, after the 8-pin connector was introduced? I didn't see anything in those documents that says this is required, but as someone pointed out earlier in the thread, most modern PSUs do have 3 12V leads on their 6-pin connections.

I guess my next question is this: Apple has been shipping Power Mac and Mac Pro systems with 2 6-pin connectors since 2003 (Power Mac G5) and 2006 (Mac Pro). This is 4-5 years before the introduction of the new 8-pin connector in 2008. Given how stagnant the design has been, do we think that they'd update their motherboard design for say the 2009 model? I don't know, which is why I've been asking for more details about the technical specs that revelstudios has been quoting.

Regarding your questions, this is exactly what I've been asking for. revelstudios has quoted some very specific numbers. I'd like to understand where those numbers came from. I'll admit, I was initially offended and my posting quality suffered, but I'm over it and am genuinely trying to learn more about this.
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Old Dec 13, 2012, 12:52 PM   #105
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Originally Posted by Asgorath View Post
Some of my confusion or misunderstanding stems from the fact that I was not aware that the 6-pin connection usually has 3 12V leads. Is this a new thing, after the 8-pin connector was introduced? I didn't see anything in those documents that says this is required, but as someone pointed out earlier in the thread, most modern PSUs do have 3 12V leads on their 6-pin connections.

I guess my next question is this: Apple has been shipping Power Mac and Mac Pro systems with 2 6-pin connectors since 2003 (Power Mac G5) and 2006 (Mac Pro). This is 4-5 years before the introduction of the new 8-pin connector in 2008. Given how stagnant the design has been, do we think that they'd update their motherboard design for say the 2009 model? I don't know, which is why I've been asking for more details about the technical specs that revelstudios has been quoting.

Regarding your questions, this is exactly what I've been asking for. revelstudios has quoted some very specific numbers. I'd like to understand where those numbers came from. I'll admit, I was initially offended and my posting quality suffered, but I'm over it and am genuinely trying to learn more about this.
6 pin PCI-Express has ALWAYS had 3 12v pins in its specs. The catch is that 1 pin is optional. The standard came about in 2003 and honestly I, nor has anyone else apparently found a PSU that only has 2 +12v in a 6 pin. But if you dig hard enough you can probably fine one.

Now as to PSU on the Mac Pro. The G5 uses a totally different one so not even going to touch on it. The 2006-2007 uses a Delta 980w PSU. The 2008-current also uses a Delta 980w PSU, however it is a different part number and referred to as v2. Now I don't know what the difference between the two are, but it likely has to do with the PCI-Express 2.0 specifications.

edit: The newer Mac Pro PSUs seem to have more amps on the +12v.

Last edited by lixuelai; Dec 13, 2012 at 01:04 PM.
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Old Dec 13, 2012, 01:30 PM   #106
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1. Is every single person who tries a 7xxx card in 10.8.3 drivers going to start their own new thread titled "I too confirm that it works". Isn't it usually best to put a post in the OP post? Unless of course you need more attention than most.

2. Until someone comes up with hard facts beyond those known, using a 6 to 8 pin is like plugging all your Christmas lights into a single outlet with hard wired cube taps. It'll probably work, but who knows? And if and when it stops working, the smell of smoke will be in the air and it will be too late for something. The GPU? The logic board? The PSU? If you like that hint of danger, that thrill of GAMBLING, the whiff of burned electronics, GO FOR IT !!!!

FWIW, I got a 7950, it is nearly as fast as 7970 and works with 2 @ 6 pins. Argument over. I guess I just need to start my own new personal "I too can re-confirm that my own previous discovery was correct" thread.

Maybe I'll even make arrogant, "I know better than you guys" sorts of statements with nebulous, unproven claims so I get more responses.
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Old Dec 13, 2012, 01:38 PM   #107
lixuelai
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Originally Posted by MacVidCards View Post
1. Is every single person who tries a 7xxx card in 10.8.3 drivers going to start their own new thread titled "I too confirm that it works". Isn't it usually best to put a post in the OP post? Unless of course you need more attention than most.

2. Until someone comes up with hard facts beyond those known, using a 6 to 8 pin is like plugging all your Christmas lights into a single outlet with hard wired cube taps. It'll probably work, but who knows? And if and when it stops working, the smell of smoke will be in the air and it will be too late for something. The GPU? The logic board? The PSU? If you like that hint of danger, that thrill of GAMBLING, the whiff of burned electronics, GO FOR IT !!!!

FWIW, I got a 7950, it is nearly as fast as 7970 and works with 2 @ 6 pins. Argument over. I guess I just need to start my own new personal "I too can re-confirm that my own previous discovery was correct" thread.

Maybe I'll even make arrogant, "I know better than you guys" sorts of statements with nebulous, unproven claims so I get more responses.
While it is indeed a lot of guesswork in trying to estimate the amount of amps the 6 pin can handle on the Mac Pro, there is no guesswork involved when measuring the power consumption of the card against currently used cards on the Mac Pro. It just so happens that the HD7970 has near identical power consumption compared to the GTX570...which you sell.
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Old Dec 13, 2012, 01:39 PM   #108
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Originally Posted by lixuelai View Post
edit: The newer Mac Pro PSUs seem to have more amps on the +12v.
Source? Are you measuring the current on the 6-pin connector on the motherboard, or is this coming from documentation somewhere?
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Old Dec 13, 2012, 01:44 PM   #109
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Source? Are you measuring the current on the 6-pin connector on the motherboard, or is this coming from documentation somewhere?
I closed the page and am too lazy to find it again since it is a moot point anyway. The ability of the PSU to handle the +12v amps was never in question. It is how much the motherboard can withstand that is in question.
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Old Dec 13, 2012, 01:55 PM   #110
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Originally Posted by lixuelai View Post
While it is indeed a lot of guesswork in trying to estimate the amount of amps the 6 pin can handle on the Mac Pro, there is no guesswork involved when measuring the power consumption of the card against currently used cards on the Mac Pro. It just so happens that the HD7970 has near identical power consumption compared to the GTX570...which you sell.
Whether I sell eggplants, petunias, or 570s has nothing to do with how many power connections are on 7970.

So your view is that AMD included 8 pin connector entirely, 100% as decoration? OK, that kind of follows OPs logic.

7950 has 2 @ 6 pins, I guess AMD didn't think it needed as much finery. I am merely pointing out that for people who want a 7xxx card with GPU horsepower with absolutely 0% (ZERO) risk of trace failure, the 7950 is a win/win.

The people who ruin their logic boards rarely come and proudly post about their stupidity. If you dig deep enough in Cindori's posts, I think you will see that he burned one up doing some GPU buggery/pokery. Most of the time, it would be fine. But if 1/1000 will blow up in a year, then it is irresponsible of people who have 10,000 (totally ballpark) or more readers to recommend something if that could lead to 10 blown logic boards.
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Old Dec 13, 2012, 02:12 PM   #111
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Originally Posted by lixuelai View Post
While it is indeed a lot of guesswork in trying to estimate the amount of amps the 6 pin can handle on the Mac Pro, there is no guesswork involved when measuring the power consumption of the card against currently used cards on the Mac Pro. It just so happens that the HD7970 has near identical power consumption compared to the GTX570...which you sell.
That's great, but this thread is about the 7970 GHz Edition, which happens to draw nearly 40 watts more under load than the 7970.
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Old Dec 13, 2012, 02:14 PM   #112
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Originally Posted by MacVidCards View Post
Whether I sell eggplants, petunias, or 570s has nothing to do with how many power connections are on 7970.

So your view is that AMD included 8 pin connector entirely, 100% as decoration? OK, that kind of follows OPs logic.

7950 has 2 @ 6 pins, I guess AMD didn't think it needed as much finery. I am merely pointing out that for people who want a 7xxx card with GPU horsepower with absolutely 0% (ZERO) risk of trace failure, the 7950 is a win/win.
Similarly you can ask why did AMD include a 6 pin to 8 pin adapter.

Anyway nowhere did I claim it is 100% decoration. However that is probably closer to the truth than you think. it is ironic that there are HD7970 GHZ editions that uses 2x 8 pins and HD7950s with 1x 6pin + 1x 8pin. Must need all that juice!

I am not going to argue against the HD7950 being a good choice. After all it is and better bang for the buck. However just because the HD7970 has 1x6 pin + 1x8 pin doesn't mean your chance of frying your traces are higher than say the GTX570 with 2x 6 pin. Now if everyone also complained about the GTX570 drawing 300w max then it would be a different story.

Quote:
Originally Posted by theSeb View Post
That's great, but this thread is about the 7970 GHz Edition, which happens to draw nearly 40 watts more under load than the 7970.
True, but my reply was to a post that made no mention of HD7970 GHZ but 6 to 8 pin in general.

Last edited by lixuelai; Dec 13, 2012 at 02:22 PM.
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Old Dec 13, 2012, 02:30 PM   #113
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Originally Posted by lixuelai View Post
Similarly you can ask why did AMD include a 6 pin to 8 pin adapter.
....

it is ironic that there are HD7970 GHZ editions that uses 2x 8 pins and HD7950s with 1x 6pin + 1x 8pin. Must need all that juice!
.
Because, in theory, the graphics card should be able to down clock itself or shut down when it needs more power than a 6 pin + 6 pin can supply. We know though that this isn't always the case and with the Mac Pro, we have additional complications and black holes in terms of specifications.


Quote:
For example, if a graphics card needs a full 300 W and has both an eight-pin and six-pin connector on board, if you were to attach two six-pin power supply connectors, the card would “sense” that it had only 225 W available and, depending on the design, it could either shut down or operate in a reduced functionality mode.
http://www.tomshardware.com/reviews/...e,3061-12.html
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Old Dec 13, 2012, 02:32 PM   #114
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Excellent thread evolution. Now it's more interesting than OP

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Originally Posted by Asgorath View Post
Source? Are you measuring the current on the 6-pin connector on the motherboard, or is this coming from documentation somewhere?
It's printed on PSU label. In general 2006-2007 PSUs have 11-18A on 12V depending on line (V1-V6), 2008+ do have 18A on all 12V lines.
But as lixuelai said, it's not a problem here.

Quote:
Originally Posted by Concorde Rules
The questions we need answering are:

1. The rating of the backplane traces
2. The rating of the mini 6-pin adapter on the backplane.
3. If there is any redundancy in the backplane's traces.
2. Molex Micro Fit 3.0 connectors are rated up to 5A per circuit: http://www.molex.com/elqNow/elqRedir...87650-5984.PDF

IDK where to find answers for Q.1&2. Schematics of MP backplane board aren't so common in the web.

Looking on backplane board itself won't help I'm afraid, because AFAIK there are few layers of traces on modern boards. We only see 2 outer layers.
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Old Dec 13, 2012, 02:35 PM   #115
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Because, in theory, the graphics card should be able to down clock itself or shut down when it needs more power than a 6 pin + 6 pin can supply. We know though that this isn't always the case and with the Mac Pro, we have additional complications and black holes in terms of specifications.




http://www.tomshardware.com/reviews/...e,3061-12.html
That would be true if you are plugging in the 6 pin directly into the 8 pin socket on the card. However the 6 pin to 8 pin adapter defeats that mechanism.
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Old Dec 13, 2012, 02:35 PM   #116
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This will be my last post in this one.

I can state with absolute certainty that at least 200+ people are running GTX570s in their Mac Pros and not ONE has had trouble with traces burning.

If AMD has choosen to spend extra $$$ putting plugs on theirs cards just to create that image that they are bigger power hogs then they actually are, great marketing idea !!!!

As has been pointed out at least 10 times already, using a 6 to 8 pin adapter makes far more sense when there is a nice fat wire coming from a $75 power supply to the GPU. Not such a good idea when the "wire" is a strip of metal of varying width that is thin like a sheet of paper and is running through a $1000 Logic Board. But if burning up $1K is the same as burning up $75 to you, good for you.

It all boils down to driving 85 in a 65. Yes, you can do it for years and never get a ticket. And yet somehow, there is always some poor sap sitting at the side of the road signing for theirs. But hey, keep going 85 and keep taking your chances. Just don't tell everyone that driving 85 is a good idea because they won't ever get a ticket.
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Old Dec 13, 2012, 02:40 PM   #117
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Similarly you can ask why did AMD include a 6 pin to 8 pin adapter.
Right, as discussed earlier, it's a PC card and not specifically designed for the Mac Pro. Every PC I've seen has a direct cable connection from the PSU to the GPU, rather than running through traces on the motherboard. This whole discussion revolves around whether those traces can handle more than the rated 75W for a standard 6-pin PCIe connection.
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Old Dec 13, 2012, 02:43 PM   #118
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Right, as discussed earlier, it's a PC card and not specifically designed for the Mac Pro. Every PC I've seen has a direct cable connection from the PSU to the GPU, rather than running through traces on the motherboard. This whole discussion revolves around whether those traces can handle more than the rated 75W for a standard 6-pin PCIe connection.
And my point all along is that whether it is 6 pin or 8 pin makes zero difference. The actual power draw matters. GTX570 has 2x 6 pin and can hit over 300w.

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Originally Posted by MacVidCards View Post
I can state with absolute certainty that at least 200+ people are running GTX570s in their Mac Pros and not ONE has had trouble with traces burning.
Great! Now we can logically conclude that a card with near identical power usage aka the HD7970 should have no issues running in a Mac Pro via 6 pin to 8 pin.
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Old Dec 13, 2012, 02:54 PM   #119
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And my point all along is that whether it is 6 pin or 8 pin makes zero difference. The actual power draw matters. GTX570 has 2x 6 pin and can hit over 300w.
Sure, but then we circle back to the fact that the connections are rated for 75W of power draw. I believe the TDP of the 570 is 219W, so if it can pull 300W while running FurMark, how much do you think a 275W TDP 7970 will pull? It's pretty clear that an app like FurMark can cause cards to pull more than their TDP, which is why AMD and NVIDIA (or at least NVIDIA, from what I've read) will manually throttle the cards when FurMark is detected because people have literally destroyed their cards while running the app.

Here's a link from 2009, for example:

http://www.geeks3d.com/20090916/furm...s-intentional/

So, that means:

- 570 is rated for 219W but can pull 300W with FurMark (+81W over TDP).
- 7970 GHz Edition is rated for 275W.
- Assuming a similar amount of overdraw, that could put the 7970 GHz Edition at 275 + 80 = 355W while running FurMark, assuming the driver isn't manually throttling the card.

So, that could very well mean the card pulls 130W more than the Mac Pro can handle, if the 6-pin connections really are only designed for 75W.
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Old Dec 13, 2012, 02:55 PM   #120
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Sure, but then we circle back to the fact that the connections are rated for 75W of power draw. I believe the TDP of the 570 is 219W, so if it can pull 300W while running FurMark, how much do you think a 275W TDP 7970 will pull? It's pretty clear that an app like FurMark can cause cards to pull more than their TDP, which is why AMD and NVIDIA (or at least NVIDIA, from what I've read) will manually throttle the cards when FurMark is detected because people have literally destroyed their cards while running the app.

Here's a link from 2009, for example:

http://www.geeks3d.com/20090916/furm...s-intentional/

So, that means:

- 570 is rated for 219W but can pull 300W with FurMark (+81W over TDP).
- 7970 GHz Edition is rated for 275W.
- Assuming a similar amount of overdraw, that could put the 7970 GHz Edition at 275 + 80 = 355W while running FurMark, assuming the driver isn't manually throttling the card.

So, that could very well mean the card pulls 130W more than the Mac Pro can handle, if the 6-pin connections really are only designed for 75W.
The HD7970 GHz actually pulls less running Furmark.

Source: techpowerup, one of the few sites that measure card power consumption, not overall system.
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Old Dec 13, 2012, 03:01 PM   #121
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The HD7970 GHz actually pulls less running Furmark.

Source: techpowerup, one of the few sites that measure card power consumption, not overall system.
Right, because the AMD Windows driver is throttling the card when FurMark is detected. Are you sure the same protections are in place on the Mac side? FurMark was only just released for the Mac, right?
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Old Dec 13, 2012, 03:07 PM   #122
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Revelstudios, why don't you simply download FurMark and measue the power draw?

I've been following this thread all the time and I must say I'm quite amused.
I am one the guys that own a MVC GTX570, I've been playing Battlefield 3 for about 10h straight (lol, LAN party) while the card had 99% usage, and my Mac still works :P

I must say, if revelstudios likes to have a 7970, why don't you simply let him? Although I have a heard time understanding his calculations...
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Old Dec 13, 2012, 03:07 PM   #123
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Right, because the AMD Windows driver is throttling the card when FurMark is detected. Are you sure the same protections are in place on the Mac side? FurMark was only just released for the Mac, right?
AMD hasn't throttled Furmark via drivers for years. If there is any throttling done it is done by the card itself. I believe AMD has a fancy name for it which I cannot remember.
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Old Dec 13, 2012, 03:14 PM   #124
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If AMD has choosen to spend extra $$$ putting plugs on theirs cards just to create that image that they are bigger power hogs then they actually are, great marketing idea !!!!
It seems to me that power connectors are more of a decision by the card manufacturer than the chipset manufacturer. There are plenty of 660's and 670's with 2x 6 pin power plugs, and some with 1x 6 and 1x8.

Here is an example of the 7950 that you said has absolutely 0% (ZERO) chance of trace failure with 1x 6 pin and 1x 8 pin. So you're saying that the Sapphire 7950 will cause trace failure because it has one 8 pin connector, but this XFX 7950 with a higher core clock won't because it's 2x 6pin??
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Old Dec 13, 2012, 03:17 PM   #125
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AMD hasn't throttled Furmark via drivers for years. If there is any throttling done it is done by the card itself. I believe AMD has a fancy name for it which I cannot remember.
Ahh that's right, good to know. I'd forgotten that the power throttling moved to the GPU board itself with the latest generation(s) of cards.

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Quote:
Originally Posted by El Awesome View Post
I must say, if revelstudios likes to have a 7970, why don't you simply let him? Although I have a heard time understanding his calculations...
The OP is of course free to run whatever he likes. My questions have simply revolved around his assertion that the power draw was not an issue, particularly given my (and many others') understanding of what the Mac Pro can provide via the 6-pin connectors on the motherboard.
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