Confirmed AMD Radeon HD 7970 GHz Edition Running on Mac Pro

blackwoodfx · Dec 13, 2012

MacVidCards said:
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.

Thanks for your completely unnecessary and inaccurate contribution here, MacVidCards.

I just want to point out, I've also been one of your customers. I purchased a GTX 570 from you on August 18, 2012 ($558 on eBay.com BuyItNow, which by the way, is about $125 MORE than what I spent on our AMD Radeon 7970 GHz Editions). After a few weeks of thorough testing and discussing with the rest of my artists, we decided we didn't like the performance compared to the 7970 or the extremely noisy fans.

And now that I read this comment here, I don't particularly care for you or how you handle customers either. So **** you too. Enjoy steering people away from cheaper, better performing cards that work absolutely fine and into your business. Apparently that's the goal here.

As another poster already pointed out, you sell cards with the exact same power draw as the 7970.

Just one more reason for me to not bother coming back here. Adios.

wonderspark · Dec 13, 2012

This thread reminds me of

theSeb · Dec 13, 2012

lixuelai said:
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.

Well, I am going to eat my hat. I was not aware of this

El Awesome · Dec 13, 2012

darkcoupon said:
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??

As far as I understood it, if the card reaches the 2x6pin power limit, it will throttle itself down. Now, if you have one 8pin, the card doesen't throttle down and draws more and more power from the traces. So therefore yes, you're right.
Remember, the Mac Pro is still a very special case! These GPUs aren't build for it. In a regular PC, this is really no matter!

666sheep · Dec 13, 2012

El Awesome said:
As far as I understood it, if the card reaches the 2x6pin power limit, it will throttle itself down. Now, if you have one 8pin, the card doesen't throttle down and draws more and more power from the traces.

Not exactly. Card will throttle itself when it will reach its own (factory defined) power limit, no matter what plugs it's using (as long as they are properly connected -> 6pin to 6 pin, 8 pin to 8 pin, with adapter or directly).
On Win side, there are programs like MSI Afterburner which are able to tweak power limit on many cards (excluding Kepler AFAIK).

lixuelai · Dec 13, 2012

All the 8 pin does is tell the card that it is connected to a 150w rail on the PSU. Nowadays most good quality PSU (Mac Pro included) can provide that much on all its +12v rails.

Asgorath · Dec 13, 2012

lixuelai said:
All the 8 pin does is tell the card that it is connected to a 150w rail on the PSU. Nowadays most good quality PSU (Mac Pro included) can provide that much on all its +12v rails.

Again, the issue is not whether the PSU can handle it, it's the traces on the motherboard that deliver power to the 6-pin connections. It'd be pretty easy for Apple to just use a new PSU with each refresh of the Mac Pro, but redoing the motherboard design is a whole other kettle of fish.

lixuelai · Dec 13, 2012

Asgorath said:
Again, the issue is not whether the PSU can handle it, it's the traces on the motherboard that deliver power to the 6-pin connections. It'd be pretty easy for Apple to just use a new PSU with each refresh of the Mac Pro, but redoing the motherboard design is a whole other kettle of fish.

I have brought up that point numerous times already and I won't repeat it. But what you are referring to is not what I was responding to.

darkcoupon · Dec 13, 2012

I'm starting to think this "collective fact" that 8pin power connectors always draw 150w is a load. If there are cards out there with the same chipset that have different power connectors, such as the 7950 examples in my last post, it has to be true that not all 8pin connectors will draw 150w unless they HAVE to(i.e. overclocking, etc..)

lixuelai · Dec 13, 2012

It is pretty common knowledge in DIY PC scene that 8 pin is not really necessary. However people still want more 8 pins on their card (I am a sucker for it too) because they think 8 pin equates to more overclocking potential. It is pretty much a tradition now that the top cards from AMD or Nvidia have an 8 pin whether they need it or not (good example is HD7970 and GTX680. GTX680 draws 180w peak and 226w running Furmark).

darkcoupon · Dec 13, 2012

Also FWIW, this guy has been selling these Mac 6pin to 8pin cables to connect 6+8pin cards to the MP for quite a while now. Looks like it just takes 3x 12v and 3x ground to 3x 12v and 5x ground. I'd like to know how that cable would be able to draw any more power than a standard 6pin.

ActionableMango · Dec 13, 2012

darkcoupon said:
Also FWIW, this guy has been selling these Mac 6pin to 8pin cables to connect 6+8pin cards to the MP for quite a while now. Looks like it just takes 3x 12v and 3x ground to 3x 12v and 5x ground. I'd like to know how that cable would be able to draw any more power than a standard 6pin.

This appears to be no different than using a 6-pin to 8-pin adapter.

Asgorath · Dec 13, 2012

ActionableMango said:
This appears to be no different than using a 6-pin to 8-pin adapter.

And he specifically states that the cables are only rated to 110W, and that the plugs themselves are only rated for 75W.

darkcoupon · Dec 13, 2012

ActionableMango said:
This appears to be no different than using a 6-pin to 8-pin adapter.

Asgorath said:
And he specifically states that the cables are only rated to 110W, and that the plugs themselves are only rated for 75W.

EXACTLY. So how can it be proven that other 6-8pin adapters aren't rated the same?

darkcoupon · Dec 13, 2012

This comes straight from the site I linked to:

These LONGER and THICKER Cables have a FULL 10 inches of wire BETWEEN the connectors (Over-All Length of 11-3/8 inches), and are made with 18AWG wire (rated for 110 watts). Although the Mac Pros PCIe Aux Power Plugs are RATED at 75w, Cables with Higher Power Handling Capabilities will Run Cooler

Molex Specs for the Mini-Fit Jr. Connectors show 20AWG as the Largest Wire Size (But THEY CAN accommodate 18AWG Wire). Conservative 12vdc wire-use charts will show 20AWG wire as good for 70-75 watts and 18AWG for 110 watts. Apple Specs for the Mac Pro Motherboard Aux PCIe Power Plugs indicate they can supply 75w each (Since the Connectors for them are rated at 108w, it's likely they may be able to deliver a bit more). PCIe slots 1 and 2 can provide 75w, so for cards rated over 225w total, the 20AWG wires are a bad choice

So official Apple specs say 75W, but infact the connectors on the Mac Pro's LB are rated at 108. With cable rated at 110w, this guy is actually selling cables capable of delivering around 110w of power to the Graphics card and advocates their use for cards that require more than 225w. By those calculations at 108w per cable plug and 75w at the PCIe slot, that makes the total max output of the Mac Pro 291w.

Asgorath · Dec 13, 2012

darkcoupon said:
This comes straight from the site I linked to:

So official Apple specs say 75W, but infact the connector's on the Mac Pro's PCIe Power Plugs are rated at 108. With cable rated at 110w, this guy is actually selling cables capable of delivering around 110w of power to the Graphics card and advocates their use for cards that require more than 225w. By those calculations at 108w per cable plug and 75w at the PCIe slot, that makes the total max output of the Mac Pro 291w.

Without seeing the specs he's referring to, it's unclear if he's talking about the physical plug that is connected to the motherboard, or the motherboard traces themselves. The 108W might be the max overhead on top of the 75W spec, but again, that overhead is there for a reason. Interesting stuff, either way.

darkcoupon · Dec 13, 2012

Asgorath said:
Without seeing the specs he's referring to, it's unclear if he's talking about the physical plug that is connected to the motherboard, or the motherboard traces themselves. The 108W might be the max overhead on top of the 75W spec, but again, that overhead is there for a reason. Interesting stuff, either way.

He's talking about the plugs that are connected to the Motherboard:

Apple Specs for the Mac Pro Motherboard Aux PCIe Power Plugs indicate they can supply 75w each (Since the Connectors for them are rated at 108w, it's likely they may be able to deliver a bit more)

Apple's a smart company, I doubt they would use plugs that were rated at 108w if the Logic Board tracers were only rated at 75.

Asgorath · Dec 13, 2012

darkcoupon said:
He's talking about the plugs that are connected to the Motherboard:

Apple's a smart company, I doubt they would use plugs that were rated at 108w if the Logic Board tracers were only rated at 75.

My point is that the plugs and traces might be rated at around the ~100W mark, but that 25-35W of overhead is what they might've designed in as the reserve in case the card pulls more than the 75W spec maximum. I don't think anyone is suggesting the components can literally only deliver 75W, I think everyone's on the same page that the hardware can physically deliver more than that. Since they are officially rated at 75W (I haven't seen anything to suggest otherwise, and that website also confirms this) all the Apple hardware qualification would surely be based around running within that spec, and from my perspective, it's a question of how safe it is to run outside of that spec for prolonged periods of time (and by that, I mean months/years not days/weeks).

Either way, 108W is certainly less than 150W, which is the full spec value of an 8-pin connection. Right?

darkcoupon · Dec 13, 2012

Asgorath said:
My point is that the plugs and traces might be rated at around the ~100W mark, but that 25-35W of overhead is what they might've designed in as the reserve in case the card pulls more than the 75W spec maximum. I don't think anyone is suggesting the components can literally only deliver 75W, I think everyone's on the same page that the hardware can physically deliver more than that. Since they are officially rated at 75W (I haven't seen anything to suggest otherwise, and that website also confirms this) all the Apple hardware qualification would surely be based around running within that spec, and from my perspective, it's a question of how safe it is to run outside of that spec for prolonged periods of time (and by that, I mean months/years not days/weeks).

Yes, but now we know that the 291w is the max power that mac pro can deliver to PCIe graphics cards. Whether running between 225w and 291w is safe is up to the user, but PC users constantly push their hardware to the limits with mixed results. I, personally, would feel safe running a 7970 with a 250w max TDP with this information.

Either way, 108W is certainly less than 150W, which is the full spec value of an 8-pin connection. Right?

On a DIY PSU that has 8-pin cables or molex connectors directly attached to the PSU, yes, the 8-pin connection may deliver 150w. But will a graphics card with an 8-pin connector and a max TDP within spec actually draw 150w of power from a source that will only deliver 108? Doubtful. Considering the fact that there are several graphics cards available with any mixture of 6 and 8-pin connectors and 6 to 8 pin converters and have max TDP around or under 250w, I'd say no. I think the max TDP is the more important factor to consider than whether the card has an 8-pin connector.

So, yes, unless I'm mistaken 8-pin connections are technically capable of delivering 150w, but will not in all cases.

Asgorath · Dec 13, 2012

darkcoupon said:
Yes, but now we know that the 291w is the max power that mac pro can deliver to PCIe graphics cards.

Assuming that the 108W connector is the lowest-rated part in the power delivery system, then sure, this seems like a valid assumption to make.

ActionableMango · Dec 13, 2012

Wouldn't a 6-pin and 8-pin pull unevenly though? I feel like all the extra wattage over 225 is being pulled from the 8-pin connector, not evenly between the two.

darkcoupon · Dec 13, 2012

Asgorath said:
Assuming that the 108W connector is the lowest-rated part in the power delivery system, then sure, this seems like a valid assumption to make.

Assuming that's the case, and the LB traces are hypothetically rated at 110w, wouldn't you say that 250-275w actually sounds like a safe limit?

And considering the fact that most graphics cards with 6+8-pin connectors draw between 150-250w max, if you're not overclocking, would you not agree that using a 6 to 8-pin converter on a 6+8 card would be safe?

VirtualRain · Dec 13, 2012

This thread is the most entertainment I've had in a while around here

One thing I'd like to throw out there, is that it's very easy for Apple to have designed the main board to carry ample current. It's neither expensive nor challenging to have seriously over designed in this regard given the board real-estate they have to work with. It's a simple matter of the size of the traces. Consider that with Apple's design it has to get at least 20 Amps of current from the top of the board (where the PSU connects) to the CPU daughter board connector alone (just to power the CPUs). Getting another 20 Amps of current to the PEG sockets is really not a big deal and there's way more incentive for them to have over-engineered this to reduce warranty claims than to have skimped on it.

Asgorath · Dec 13, 2012

ActionableMango said:
Wouldn't a 6-pin and 8-pin pull unevenly though? I feel like all the extra wattage over 225 is being pulled from the 8-pin connector, not evenly between the two.

Right, that's what I would've thought too. I'm certainly not an expert, but it seems logical that the 250W for the 7970 would be pulled as:

- 75W out of 75W from the slot itself.
- 75W out of 75W from the 6-pin cable.
- 100W out of 150W from the 8-pin cable.

If that's the case, that seems uncomfortably close to the limit of the connector.

darkcoupon said:
Assuming that's the case, and the LB traces are hypothetically rated at 110w, wouldn't you say that 250-275w actually sounds like a safe limit?

Apple designed the system to have headroom of say 35W (i.e. nearly 50% of what the spec requires). Assuming the above is correct, now you're running with a headroom of less than 10W.

I did a Google search to try and find out more information about the supposed 300W draw from a GTX 570, and found this link:

http://www.geeks3d.com/20100328/geforce-gtx-480-tortured-by-furmark-300w-and-earplugs-required/

That article is discussing the GTX 480, which also has a TDP of 250W, but was measured to pull nearly 300W while running FurMark. Granted, more modern cards have hardware protections to prevent going over the TDP (i.e. AMD's PowerTune) so who knows.

slughead · Dec 14, 2012

lixuelai said:
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.

I own one. They are not uncommon. That said, I think the majority have 3 x 12v

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