Sidebar Sidebar
Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.

Cables Needed For Video Cards in MacPro

RAMtheSSD

RAMtheSSD

macrumors regular
Original poster
Mar 23, 2013
126
22
High on a Mountain Looking for Wisdom
I am going crazy! There are gobs and gobs of information here but sometimes, sometimes often, the specific information that one is searching for is buried under tons of other info of varying complexities and lengths which one then has to read to sort the wheat from the chaff. Other times, the information is buried under the procedure for doing something else and buried so deeply that one can't find it in any kind of hurry.

So here is my "HELP!! I'M GOING CRAZY!!" question: what cables are needed for (and when you answer, please state specifically for what video card) what video card and how long must the cable be for a given Mac Pro model. (HIS R9 280; Mac Pro 4,1 box and board) Also, if the end that is miniPCIe is male or female and if the other end (6 pin PCIe?) is male or female. There are literally hundreds of cables on amazon of unknown length and unknown voltage and amperage capacity (is one to presume that all cables with the same connector are capable of carrying the same voltage and amperage? (I thought that was impossible)) and they are all labeled as if a G5 Power Mac and a Mac Pro were the same thing!

I have worked on more than a few machines in my time but when I ordered through the channels then available to me (B2B) the specs for everything one could order were explicitly displayed.

Please, anyone that can help, I ordered the card because there was only one left (from what I understand, it is very big) so I will be paying extra for S&H for the cables; if I might need an extension for either or both of the cables needed, I would like to get them all at once. Thanks

Admins (if I might suggest: posts such as this that contain vital information to common mods would serve the community best if the information was filtered and aggregated into one sub forum for the specific machine in question? I hope I am not overstepping by making this suggestion and thank you for maintaining such an indispensable forum for Macs)
 
Thanks VAGDesign, for a while there it seemed that I was going to have no help on this at all. I am still confused about one thing: everyone says 2X6 pins but they also mention the 6 pin miniPCIe to 8 pin PCIe which would seem to suggest that I need TWO of the 6 pin miniPCIe to PCIe even though the card only has 1 each; an 8pin and a 6 pin connectors. The link you sent me kicks ass but the guy is in the UK which makes shipping more than the cable LOL!
 
It seems that I know why you are so confused now. The root problem is that you get a wrong card, which is not matching the Mac Pro's spec.

Your card has a 6+8pin config, which is NOT suppose to be powered safely by the Mac Pro's internal power only.

A 6 pin can draw up to 75W (assuming the card is in stock config, without OC).

A 8 pin can draw up to 150W (same assumption).

However, the mini 6 pin onboard can only provide 75W each safely.

That's why if there is ever a 8pin connection on your card, someone here may advice you to use a 2x6pin to 8pin for that particular port.

In your case, since it's a 6+8 pin config. You have few choices.

1) use extra PSU, which allows you to use a normal 6pin and 8pin cable to power the card.

2) go through the PSU mod, which may not be a good choice for you by considering that it seems you are not that knowledgable in this area.

3) ignore the 75W power limit. Use a mini 6pin->6pin + a mini 6 pin->8 pin to power your card. It should work. However, it may cause permanent damage to your Mac Pro. Or not enough power for your card to work properly.

4) use abnormal cable config. e.g. a dual mini 6pin->8pin and dual SATA->6pin to power the card. Which will keep everything within limit, but not easy to get such customise cable.

TBO, no matter which option you choose, there is no simple and 100% safe way to power your card. IMO, if you have the knowledge and tool, the PSU mod option is the best, which allow you to use even a dual 8pin card without any problem. However, a single mistake during the mod may kill your Mac.

I am now only using that onboard dual mini 6pin supply to power a 7950 + R9 280, which is equals to drive a 2x8pin card. I know what I am doing. It will excess the limit when both under full load. And I am using the build in buffer which I am not supposed to touch. So far, zero issue. I did some precautionary measurement e.g. Downvolt both card, and limit their max power draw in the VBIOS. That's why I am comfortable to power the card in this way. But from my experience, these mini 6pin port can supply up to 100W without any issue.

If you are happy to use this 100W as your personal limit. Then you will have an option which is get a customise cable "dual mini 6pin-> 6+8pin" which will share the 6+8 demand across the dual mini 6pin supply. Even though technically they can draw up to 225W from the dual 6pin, it just won't happen on a stock R9 280. Also, the Mac Pro will shut itself down if you really draw too much from the mini 6 pin supply. I personally happy to push beyond the normal 75W limit as long as I didn't hit that "shut down limit" yet. And I never hit that hard limit so far.

I know that I may introduce more confusion for you now. So a quick summary.

A) there is no easy and safe way to power your 6+8pin R9 280.

B) you either get another card which is dual 6pin config, or use any other abnormal way to power the card.
 
Last edited:
  • Like
Reactions: Synchro3
Thanks H9827690 that is exactly what I needed in terms of the info. My only problem is that I bought this card precisely because, not only are people using this card right now, it is used as the example in the tutorial on the procedure to enable PCIe 2 on the card. In short order, this will be my only video card (following a flashing) so one would think there would be plenty of power since there is nothing else connected to PCIe at all. In fact, one of the people who runs it, has had it for a week or so and he did not mention anything concerning an extra power supply. I can certainly return it if need be but since this is a 7950 in disguise and that is what sapphire sells as a native Mac card, shouldn't it run with the same power demands? The only thing different between the HIS ICEQ (not the overclocked or the X2) and the 7950 is the massive heatsink as the 7950 has a comparable size fan.

You paint a very frightening picture indeed but at the same time, you ran the 7950 for some time all by itself on a machine with far far more demands on its power supply than mine albeit with only one processor but otherwise, my power supply powers only 4 HDs and an SSD (I don't even have the optical drive connected) whereas your has, not only a list, but a list of things with very high power demands so wouldn't the 7950 have caused you similar problems? I am not being either facetious or dismissive; I am taking all of this very much to heart. However, the problem I have to solve is very real to me right now (trapped on a screen by screen rendering delays) and this seemed -given how many people own either a 7950 (mac or PC) or any number of variations on the R9 280 architecture.

I really need to reread your post again and think about what I am going to do but could I draw power from another PCIe slot in some way or from the 2nd optical bay with an appropriate adapter? I doubt my card will ever come close to anything like full power draw since what I need most is the rendering capacity and the memory rather than the speed which is so far beyond what the GT120 can do that in some reviews, the bar representing the GT120 was little more than a pixel deep.
 
Incidentally, under similar circumstances on a PC (where I do have far more experience) a 1000w power supply would have a few spare connectors coming directly from the power supply and that is where I would take power and it is this lack of any other power connections that has me perplexed --it almost seems like it takes all these hacks to get the machine to its potential; one which, apparently, Apple never envisioned. My girlfriend's daughter uses a much hotter video card (the thing is in the 300w range!) with only a 750 power supply -granted on a PC. One would think a Mac Pro, given what they are used for, would be able to power a very powerful card indeed.

I await your reply with trepidation but in the meantime, I will see if I can find that dual SATA to 8 pin or 6 pin (presumably, a 6 pin to two 6 pin Y would work )
 
Is this something like what you have in mind as far as taking power from elsewhere? Like from a card in another slot with 2 SATA ports available? The SATA card I have in mind has 4 so I could do this a 6-8 adapter and power the 8 from here and do the 6 to dual 6 from the motherboard.
 

Attachments

  • 2SATA to 6pin PCIe.jpg
    2SATA to 6pin PCIe.jpg
    40.8 KB · Views: 95
Last edited:
I've got a 7950 with a 6pin + 8pin I was looking at putting into my Mac Pro.

Planning on getting either this or more likely this adapter as I already have two 6-pin cables in place and would rather just leave them as-is.

I don't think the card really draws an excessive amount of power that I would be too concerned about it.
I can report back if my machine blows up. :/
 
As an Amazon Associate, MacRumors earns a commission from qualifying purchases made through links in this post.
I must tell you the worse case before I encourage you to excess any factory limit. In fact, the PSU in the cMP is quite powerful and not the source of the trouble. The real problem is the spec of the 6pin line. It's only rated up to 75W, so if you draw anything more than that, technically you may burn the mobo. That's why we try to use all sort of mod / customeise cable to keep everything within limit.

From memory, the SATA port can provide up to 55W each, so 2 of them can provide 110W, which is well above 75W, so should be very safe, and you already found that cable. On the other hand, the dual 6pin to 8pin will provide exactly 150W. So, all problem solved.

TBO, all of these are base on worse case scenario. In real, this card won't draw anything close to that limit, especially the 8pin input. That's for very serious OC. If your card comes with the standard clock 800MHz, I really doubt will the 8pin pull anything more than 75W.
 
So It sounds like what you are saying is that I can safely try it out within the parameters of my current use (I don't play games and if I did, it would be something like flight simulator. I need the number of rendering units (faster than the GT120) and the memory) with just the two miniPCIe connectors. That being said, how would I watch the voltage draw? Short of the machine shutting down, how would I know that I need the extra power?

I am used to power supplies having multiple lines coming out of them or being modular and having ~4 open holes to draw power from by just plugging in a wire that came with the power supply but that one would not install unless one needed it. This no power out except were we let you could drive me crazy. I hope that the processor upgrade -given how mature the procedure seems to be- will only be a matter of finding the washers LOL!
 
Ok, so now I am really really going CRAZY! LOL! I went looking for 6 pin and 6 pin but ALL of the R9 280s that I've found thus far ARE 6 and 8! I had to cancel the order before (I had already cancelled it when I wrote the above) because I had hope of finding 6+6. The irony is that the Sapphire card that I will probably end up with is the same as the card that I would buy if I bought the Mac specific version but it has 6+8 so there really is no choice but to try. On the other hand, if I have to buy the PCIe card with the SATA ports because of the power draw then I might as well go for gold and get the 280x or something as hot as I can afford because whatever it is, it will be there for a while.
 
I use XFX 7950 which I flashed myself for boot screens, it needs 2x6pins, I also have a spare XFX 7970 just in case I need it in the future. I wouldn't go to a 6+8pins card on my Mac Pro. 7970 needs that and that's why I have it on the box. Better be safe than sorry.
 
You can use Hardware Monitor to watch the power consumption. And here is the sharing about my dual GPU setup. (another one at here)

Just open Hardware Monitor, let it run in the background, and then do whatever you want to stress the GPU. It will allow you to check the history of the power consumption. As you can see, it gives you the max value as well. Very straight forward.

Anyway, it seems that you've already cancel the order and looking for the correct card. Which IMO is a better option, apart from may be more time consuming.
 
Last edited:
I will be out for my birthday but it looks like I will have to suck power out of another PCIe slot. The problem is this: the sapphire 7950 MAC is >450$ and has 6+6 but the sapphire R9 280 has 6 + 8! as does the 280x so if I am going to go through the effort to find a way to suck out 100+w then, why not go for the gusto eh? Same card, just hotter -plenty of cooling capacity, that we all have in droves LOL!- and same resistors and bios configuration right?

I will be going to the store sometime Monday afternoon but I will check in beforehand to see what everyone thinks though 260w available for a 200w card should be more than safe... now, if I could pipe the heat directly out to the aluminum (conduction vs convection) with winter coming, the machine could heat up the apartment just from the video card LOL!
 
RAMtheSSD said:
I will be out for my birthday but it looks like I will have to suck power out of another PCIe slot. The problem is this: the sapphire 7950 MAC is >450$ and has 6+6 but the sapphire R9 280 has 6 + 8! as does the 280x so if I am going to go through the effort to find a way to suck out 100+w then, why not go for the gusto eh? Same card, just hotter -plenty of cooling capacity, that we all have in droves LOL!- and same resistors and bios configuration right?

I will be going to the store sometime Monday afternoon but I will check in beforehand to see what everyone thinks though 260w available for a 200w card should be more than safe... now, if I could pipe the heat directly out to the aluminum (conduction vs convection) with winter coming, the machine could heat up the apartment just from the video card LOL!
Click to expand...

If you are this worried get a reference 7950.
 
Not so much worried as careful but frustrated because there is a degree of absurdity in the entire process: a 1000w power supply but no way to take even a small fraction of that power. The ability to use up to 4 PCIe cards but a limit of 300w on the PCIe bus with the most insane thing being the ability to do crossfire (afaik under windows only) but there isn't a card such that two would not exceed the 300w limit. Ok, so add the 150 from the miniPCIe but still short 50 and the contradictions go up from there.

I found a R9 280 with 6 and 6 from Sapphire: Dual X R9 280 2 DVI, 1 DP, 1 HDMI and once the cables get here I will report on the outcome though I expect a favorable outcome given the mild overclocking coupled with a 225w TDP which I should be able to comfortably meet inPCIe+miniPCIe+miniPCIe particularly since I do not have any other cards. I am considering a PCIe SSD but I suspect that I will still be well below the 300w total power draw.

Once everything is stable I'll do the resistor (I understand this is a must?) and the flash and report further.

MacVidCards: I wish I had the money because if I had, I would have just bought it from you and avoided the entire mess in the first place.
 
Be careful, the real limitation is not the overall limit, but individual limit. Each 6 pin should not draw more than 75W, and each slot should not draw more than 75W. So, even though your card draw right at 225W after overclock. If it draw 100W from 6pin A, another 100W from 6pin B, and only 25W from the PCIe slot. You are already way excess the limitation.

In my experience, the card tends to draw lots of power from the 6 pins but nothing close to 75W from the slot. Also, the power consumption between the 2 cables is not evenly distributed. If it draw 200W in total. It may be 100W from 6 pin A, 75W from 6 pin B, and only 25W from the slot.

IMO, it is safe. As I said before, I even allow 2 mini 6 pin to power dual 7950 in my own rig. But I think you need to know this fact before you OC your card, and keep pushing it towards the 225W limit.
 
The PCIe slot can supply up to 75W as well. So 75W (from slot) + 75W (from a single 6pin) = 150W, which is more than enough for a 108W 5770.
 
You must log in or register to reply here.
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.
Top Bottom
Back