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Old Dec 11, 2012, 01:21 PM   #26
ActionableMango
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Originally Posted by DanielCoffey View Post
Not really - the card doesn't say "Mac Supported" on it and for almost all PC uses, the supplied cable will be perfectly fine. It is just on Mac Pros with the traces on the Logic Board that it shouldn't be used.
Thanks, I understand now. And thanks for explaining without being confrontational.
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Old Dec 11, 2012, 02:46 PM   #27
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Because it probably works fine when you connect one of the nice big fat cables coming out of a regular PC power supply? The major difference here is the fact that the supplemental power comes from the 2 low-profile connectors on the motherboard. These are designed for 75W each, and the power comes through the traces on the motherboard itself (not a dedicated cable from the PSU).

The point we're trying to make is that the Mac Pro is designed for a maximum of one 225W card. You're in unsupported territory if you try and drive a card that requires more than that via the slot and power cables alone. You might damage the card and/or your entire system -- for example, there's a thread over on netkas.org where a guy tried to overclock his 300W GTX 680 super-overclocked board running on Mac Pro power alone, and ended up killing it. If you want to risk your $500 card or $2500 system, go for it. Personally, I'll stick with cards that fit inside the 225W power budget.
Sorry Jack, The Mac Pro's I run are > $8,000. You might want to check the screen shots from the start of this thread, particularly if you want to present 'expert' opinions like this. That's a $450 card in a $8,000+ Mac Pro (multiple, in fact). All crushing 4K UHD video and post VFX.

And for you guys suggesting I use an external PSU -- right. Again, RTT. You might notice I posted this a little while ago:

http://forums.macrumors.com/showthread.php?t=1076970

Finally, it's rare to run into Apple guys that still believe the mystique of Apple hardware versus PC hardware. I hate to tell you friends, that line has blurred to almost non-existence. I was trying to be polite about all of this, but after the MacRumor nannies have decided to dump warning stickers all over my thread, I'm just going to lay it down: You're completely mental if you think this card is going to harm this Mac Pro.

This is the *actual* spec of the MP PSU PCI wires: 21a @ 12v = 252w with contacts rated to 36a @ 12v = 432w. That load will shutdown your system long before frying wiring or the LB.

The reason AMD will not present these cards as "Mac Ready" is because until 3 weeks ago, Apple wasn't including the drivers for the cards and AMD isn't going to suggest customers start scooping them up without official, public release driver support. To this second, you cannot run these cards without the beta software of 10.8.2+ (I've tested on both 10.8.2 and current developer release 10.8.3). Again, it's mental to suggest it's out of fear for harming a MP. You guys are ridiculous.

Stop with the goddam FUD, please. Enjoy the new hardware.
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Old Dec 11, 2012, 02:50 PM   #28
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Nobody said the wires in the PSU weren't up to the job. It was mentioned that the Logic Board traces were not rated for more than 75W.

Still... your card, your "$8000" Mac Pro. Your risk.
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Old Dec 11, 2012, 02:53 PM   #29
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Nobody said the wires in the PSU weren't up to the job. It was mentioned that the Logic Board traces were not rated for more than 75W.

Still... your card, your "$8000" Mac Pro. Your risk.
The LB is rated to the same spec.

Thanks for your permission. Vroooom!
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Old Dec 11, 2012, 02:59 PM   #30
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The LB is rated to the same spec.

Thanks for your permission. Vroooom!
I'd very much like a definitive answer on this. I was met with the same 'nanny' approach seen here and would like someone to actually provide proof the traces are not/are rated the same as the PSU wires. Anyone care to provide solid evidence? I've seen everyone and his dog have a 'solid' opinion on this but nothing actually definitive.
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Old Dec 11, 2012, 03:12 PM   #31
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The LB is rated to the same spec.

Thanks for your permission. Vroooom!
Where is your proof the backplane traces are rated to support 150W?

Not only that, the backplane has a mini 6-pin connector, which almost certainly cannot withstand 150W!!!!

Unless you can supply proof that that mini 6-pin connector and the mobo traces can support 150W then I'm afraid your playing with fire and people here will simply call you foolish.

As far as I am concerned, the absolute maximum power draw a GPU can draw in the Mac Pro is ~225W.

As an engineer, I can imagine there is a decent safety factor in the design, but 2x Reserve Factor? I think that is pushing it...

I have thought that if you merged the two 6 pins and then split them to 8 & 6 pins then your sharing the 8 pin added load over two. But then your buggering about with a 2k+ computer or a 600+ motherboard if your out of warranty.

The 7950 and I think the 670 is 90% of the performance, so why risk it?

Nice to know it works tho, it means I am a step closer to getting a 7950 in my Mac Pro.
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Old Dec 11, 2012, 03:28 PM   #32
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I'd very much like a definitive answer on this. I was met with the same 'nanny' approach seen here and would like someone to actually provide proof the traces are not/are rated the same as the PSU wires. Anyone care to provide solid evidence? I've seen everyone and his dog have a 'solid' opinion on this but nothing actually definitive.
The info I posted above is from Intel, provided to HP, which also uses backplane PSU tracing in flavors of ProLiant. Same hardware, same manufacturer, same exact specifications, processors, etc.

It's pretty amazing that guys have no problem understanding that a graphics card can handle that kind of power, and the 12v PCI wires can, but not the Apple LB or BP. Bwa?

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Originally Posted by Concorde Rules View Post
As an engineer, I can imagine there is a decent safety factor in the design, but 2x Reserve Factor? I think that is pushing it...
Wow... *slow clap* For the love of my family, may I never use anything you design or build.

----------

It's been 'great' conversing with you folks here. I appreciate all of the warning stickers and FUD'ing... Particularly when it's thrown at a guy that took the time to safely turn this stuff over and do quite a bit of burn-in and homework prior and after use, well before sharing here. I guess you guys must know better though.

My eyes and our little studio running all of this hardware [for the last many weeks] are just a figment of my imagination. Well, I'm off to get some meds and come down from this cloud.

Oh, if anyone has an Apple LB or BP that has fried PSU traces due to running a 6-pin to 8-pin connector, drop me a private message. I'd love to buy it from you and hang it on my mantle. Right next to my unicorn horn.
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Old Dec 11, 2012, 03:34 PM   #33
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Still... your card, your "$8000" Mac Pro. Your risk.
Exactly. No need to be so obnoxious, revelstudios. If you want to run your machine with a card that draw more power than the Mac Pro is officially spec'ed to provide, go for it.

All we're suggesting is a little caution when posting advice for wide consumption. Are you going to step up and provide replacement systems for any user who takes your advice, plugs in a card only to find out that you were wrong and their motherboard and/or GPU is totally fried? No? Then perhaps you should back off the "it's totally fine guys, no worries" stance.

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Oh, if anyone has an Apple LB or BP that has fried PSU traces due to running a 6-pin to 8-pin connector, drop me a private message. I'd love to buy it from you and hang it on my mantle. Right next to my unicorn horn.
Here you go, here's a guy who fried his GTX 580 that also requires more than 225W:

http://forum.netkas.org/index.php/topic,3551.0.html
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Old Dec 11, 2012, 03:44 PM   #34
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I don't understand the attitude. If I was going to behave ... like that.. I wouldn't want my business' URL in my sig.
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Old Dec 11, 2012, 04:12 PM   #35
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I don't understand the attitude. If I was going to behave ... like that.. I wouldn't want my business' URL in my sig.
You'd prefer people hide behind screen names? I'd rather people just be up front all around. I'm sorry you think I have an 'attitude' here, but I guess you didn't read the full thread and see where the condescending began. (Honestly, it doesn't matter.)

Side note; more and more forums are requiring real names for posters. I like that trend. I hope it continues.

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Here you go, here's a guy who fried his GTX 580 that also requires more than 225W:

http://forum.netkas.org/index.php/topic,3551.0.html
Thank you. From the second comment, "The MSI 580 has 2 @ 8 pin power plugs." That's 75w more than what I'm pulling and I said at the very beginning of this thread, as configured, I am 50w under the limit.
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Old Dec 11, 2012, 05:16 PM   #36
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Just want to say thank you, and I appreciate the information being presented from both sides.

I'm still hiding out in 10.6.8 due to the fact that it's running great for me with a 5870 on CS5.5 and CS6, but I'll be paying attention to things such as this, and possibly taking the plunge into 10.8 and a 7970 sometime.

I run a W3680, an 1880ix-12 Areca RAID card and a Caldigit FASTA-6GU3 in my 4,1... but I don't know how many watts that would add up to, combined with a 7970. Any insights or opinions on that, revelstudios?
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Old Dec 11, 2012, 05:27 PM   #37
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Here you go, here's a guy who fried his GTX 580 that also requires more than 225W:

http://forum.netkas.org/index.php/topic,3551.0.html
Maybe I have misinterpreted that thread, but it seems to be that this guy ruined his gear when he decided to simultaneously overclock and overvoltage his card, and that it worked fine before he did that.
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Old Dec 11, 2012, 05:49 PM   #38
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You'd prefer people hide behind screen names? I'd rather people just be up front all around. I'm sorry you think I have an 'attitude' here, but I guess you didn't read the full thread and see where the condescending began. (Honestly, it doesn't matter.)
I'm certainly not trying to be condescending, and neither is DanielCoffey from what I've seen. We're both pointing out that the Mac Pro is officially spec'ed to deliver a maximum of 225W to a PCIe card, based on the fact it only has 2 6-pin connectors on the motherboard.

Personally, I am never going to recommend that people use a 6-pin to 8-pin converter cable. If you or they decide that you're okay running your machine out of spec, that's great. Given the fact that it is out of spec, and that there's no guarantee that something bad won't happen if you do, I think it's a little bold to just say "it's fine, don't worry about it". Destroying an $8000 system might not mean anything to you, but other folks might not want to take the risk since they might not be able to replace the system. That's all we're trying to say -- as long as you understand the risk, you are all free to do whatever you like.
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Old Dec 11, 2012, 06:38 PM   #39
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Revelstudios,

I hope you will post an update after you've been pushing these cards hard for a few weeks, and again later for a few months. Whatever happens, whether there are problems or not, I'm sure the examples will be valuable to the community.

Personally my needs are humble and I don't see myself exceeding 2x6-pin power. However, as an enthusiast, I cannot help but be interested in what's going on at the boundaries.
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Old Dec 11, 2012, 06:52 PM   #40
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I'm interested as well, but I noticed that he HAS run them for "many weeks" now, as he said a few posts back. I've had an overclocked PC fry on me in the past after a couple years of hard use, so it's possible that the card could cause a problem after prolonged use, in my opinion.

Thing is, I'm already beyond my AppleCare on my 4,1 Mac Pro, and I've earned enough money several times over to buy a new one if it dies, so I wouldn't be too crushed if I had to get a new part or two down the road. At the rate Apple is keeping the Mac Pro up to date, I'll most likely buy a PC if this thing dies, anyway. In such a case, I'll be free to use any PC card.

In the meantime, extending the capabilities of a Mac Pro with new GPUs and such is just saving me money otherwise spent on building a new PC.
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Old Dec 11, 2012, 07:22 PM   #41
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I'd very much like a definitive answer on this. I was met with the same 'nanny' approach seen here and would like someone to actually provide proof the traces are not/are rated the same as the PSU wires. Anyone care to provide solid evidence? I've seen everyone and his dog have a 'solid' opinion on this but nothing actually definitive.
I've written a how-to guide on external PSUs in the Mac Pro and I'm convinced there's no definitive source on what the rating is. There is only anecdotal stories of running dual 8 pin (150w/cable x 2) cards or even multiple cards off of the motherboard tracers and frying the Mobo.

Here's an article explaining the difference between 6 pin and 8 pin:
http://www.tomshardware.com/reviews/...e,3061-12.html

Who knows, different MPs could have different tolerances. I just looked at how much power the 5870 eats and make sure my card takes around that much before using 6 to 8 pin adapters (on the assumption Apple wouldn't make a card that could kill their own computer). I ended up using an external PSU to run my GTX 670, but that's only because I have a 2nd card in there

I trust that the GTX670 can run off the motherboard tracers (unless manually overclocked), but the 7970 uses 47% more power.

All we know is, people have fried their mobos with less than 150 watts/cable (how much less, we don't know)...

In short: we don't know, but OP's confidence that he is safe is really ridiculous. 7970 draws a lot of power. I would sure as hell not use a 7970 drawing power through the on-board 6 pins without knowing the limits of the Mobo tracers. A 2nd PSU, however, is clearly okay.

Perhaps someone could take an old Mac Pro mobo and crank the power up until it melts?

Last edited by slughead; Dec 11, 2012 at 08:18 PM.
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Old Dec 11, 2012, 07:23 PM   #42
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You'd prefer people hide behind screen names?
No, I'd simply rather people act the same way as they would in person. People tend to get a lot more aggressive than they would face to face.

I did follow the whole thread, and it seemed that others wanted to take a cautious approach and you took offense that people didn't simply take your word for it.
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Old Dec 11, 2012, 07:49 PM   #43
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I don't understand why people risk their expensive hardware on a $60 power supply and 10 minutes. All you need is a paperclip and a power supply and you don't ever have to worry about power draw.
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Old Dec 11, 2012, 08:04 PM   #44
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In short: we don't know, but OP's confidence that he is safe is really ridiculous. 7970 draws a lot of power. I would sure as hell not use a 7970 drawing power through the on-board 6 pins without knowing the limits of the Mobo tracers. A 2nd PSU, however, is clearly okay.
Right, my main concern with the OP's position is that if the system were designed to safely deliver 150W per connector on the motherboard, why aren't the connectors and cables already 8 pins? I believe my first reply was basically "our standard advice has been to use an external PSU if the card has one or more 8-pin connectors", which I still stand by.

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In fact, the only difference between a 6 pin and an 8 pin connection is the number of grounds. Both use 3x 12v rails. The 6 pin has 3 grounds and the 8 pin uses 5. Pins 1-3 are hot, 4-6 are ground + 7-8 ground. So those two extra pins are grounds only.
I'm not an electrical engineer and my memory of this stuff is pretty faded at this point, but isn't the power a function of both the voltage and current? 3 x 12V rails is all well and good, but if the traces are only designed to deliver enough current to provide 75W on those 3 rails, and you pull double that amount of current, aren't you in danger of damaging the traces? I'm sure there's some amount of headroom on top of the 75W, but it seems potentially dangerous to go from running within spec to blowing that headroom and running near/at/past the maximum.

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Here's an article explaining the difference between 6 pin and 8 pin:
http://www.tomshardware.com/reviews/...e,3061-12.html
Thanks for the link. I found this particularly interesting:

Quote:
The six-pin connector uses two +12 V wires to carry up to 75 W, whereas the eight-pin connector uses three +12 V wires to carry up to 150 W.
So there really is a difference between the connections.
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Old Dec 11, 2012, 08:09 PM   #45
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Right, my main concern with the OP's position is that if the system were designed to safely deliver 150W per connector on the motherboard, why aren't the connectors and cables already 8 pins? I believe my first reply was basically "our standard advice has been to use an external PSU if the card has one or more 8-pin connectors", which I still stand by.
Well we already know it can't handle 150watts per connector, since the Netkas thread appeared where the guy with the 580 managed to fry his hardware. The 580 likely didn't exceed specifications of the 8 pin connector (safeguards are in place), the MP couldn't handle it.

Of course we're not coming close to that kind of power here, but we still don't know how much it takes to kill the tracers, nor over what period of time. It may work 9 times out of 10, but if you're playing games for 10 hours six months from now, that could be the day where a wild new character shows up and pushes your card over tolerances of the tracers.

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So there really is a difference between the connections.
Remember that those are just rated tolerances. Most PSU makers exceed those tolerances and most card makers run under those tolerances.

That's why the GTX670 has an 8 pin even though by default it doesn't need it --for overclocking and "just in case"

Also, many PSU makers including Apple have 3 x 12 volt leads on their 6 pin, which is 1 more than the standard. Who knows what the 3rd pin can handle

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Old Dec 11, 2012, 08:09 PM   #46
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Well we already know it can't handle 150watts per connector
The OP doesn't seem to believe this Your point is a good one, and pretty much exactly what I've been saying -- it might work for him now, but out of spec is out of spec. I'm with you on the external power supply thing, your guides make it so easy to do and the risks just aren't worth it for me.
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Old Dec 11, 2012, 08:11 PM   #47
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Same page. Not sure why you're suggesting I'm not aware of this. There's no magic here. It's pulling 75w+150w on those lines. However, it's not exceeding the design spec at all. In fact, the only difference between a 6 pin and an 8 pin connection is the number of grounds. Both use 3x 12v rails. The 6 pin has 3 grounds and the 8 pin uses 5. Pins 1-3 are hot, 4-6 are ground + 7-8 ground. So those two extra pins are grounds only. They tell the graphics card it's ok to draw 150w -- which it is. Exceeding the design spec? Not at all.
You're wrong, The standard 6 pin assignment has only two 12 volt poles in addition to the grounds. It just happens that most PSU makers add a 3rd pin.

Source:
http://www.tomshardware.com/reviews/...e,3061-12.html

Also, once again: It is not about the physical limitation of these wires: you're right. This is about Apple's choice of putting the power through tracers on the motherboard, which you have no reason to think can run the 7970's level of current usage.

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Old Dec 11, 2012, 10:43 PM   #48
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All we're suggesting is a little caution when posting advice for wide consumption. Are you going to step up and provide replacement systems for any user who takes your advice, plugs in a card only to find out that you were wrong and their motherboard and/or GPU is totally fried? No? Then perhaps you should back off the "it's totally fine guys, no worries" stance.
I think the purpose of a forum such as this is exactly what the OP did - give real world experience. The fact the you or anyone else think the topic is not advisable or risky is no reason to not post this information. This is what public forums on the internet are all about. Nobody is stopping nay-sayers from posting their opposition. Any one who is reading this forum and doesn't realize that common sense should be used probably shouldn't be reading or contributing. Caveat emptor.

My 2009 Mac Pro has more than paid for itself many times over and I for one truly appreciate the OP giving up his experience and it is of no risk to me to try it. If it burns up, so what. I'll buy a new one and the cycle will continue.

Thanks for the info revelstudios. Most of us are intelligent enough to appreciate your post for what it is.
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Old Dec 12, 2012, 01:07 AM   #49
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Say aye.....

With the hundreds (thousands?) of users here I'd like to hear an "Aye" from everyone who has fried a logic board trace from using a 6 to 8 pin adapter.....

Please speak up !


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Old Dec 12, 2012, 02:36 AM   #50
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Well we already know it can't handle 150watts per connector, since the Netkas thread appeared where the guy with the 580 managed to fry his hardware. The 580 likely didn't exceed specifications of the 8 pin connector (safeguards are in place), the MP couldn't handle it.

Of course we're not coming close to that kind of power here, but we still don't know how much it takes to kill the tracers, nor over what period of time. It may work 9 times out of 10, but if you're playing games for 10 hours six months from now, that could be the day where a wild new character shows up and pushes your card over tolerances of the tracers.

----------



Remember that those are just rated tolerances. Most PSU makers exceed those tolerances and most card makers run under those tolerances.

That's why the GTX670 has an 8 pin even though by default it doesn't need it --for overclocking and "just in case"

Also, many PSU makers including Apple have 3 x 12 volt leads on their 6 pin, which is 1 more than the standard. Who knows what the 3rd pin can handle
A stock 670 won't even have an 8 pin, just the pair of 6's. heck, my GTX680 has a pair of 6 pin connectors.
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