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ava10

macrumors newbie
Original poster
Mar 2, 2020
8
0
for MacPro 5,1. I would like to confirm if I use the 2 six pin that on the mother board to 1 eight pin on the card. I will have no power issues that hinder the performance or damage the motherboard a person on YouTube suggested.
 

MarkC426

macrumors 68040
May 14, 2008
3,700
2,097
UK
From the GPU wiki
https://forums.macrumors.com/threads/gpu-compatibility-list-for-cmp.2174600/

22. AMD Radeon HD 7970 / R9 280X 3 Gb
Performance: 100% RPI. A very good card for power / price / performance ratio. ~ 10% faster than GTX 680 2 Gb, has more memory. Supports Metal 2 (Mojave).
Power consumption: 6 pins + 8 pins. Additional power is recommended, as minimum - from SATA port. Possible scheme: 6 pins -> 8 pins and 6 pins + SATA -> 8 pins via dual 6 pins to 8 pins adapter).
Outs: as usual card has DL-DVI + two mDP + HDMI.
Compatibility: DirectX 12.0, OpenGL 4.6, Metal 2.
Other: as usual occupies 2 slots. There are Gigabyte and Sapphire versions that have two slots brackets but don't block the nearest PCIE slot. There are cards with dual BIOS (mac / PC). There are cards with different cooling system. There is an overclocked version AMD Radeon HD 7970 GHZ which is ~ 7% faster.
Unflashed (PC version): additional information is needed, can be flashed.
 

ava10

macrumors newbie
Original poster
Mar 2, 2020
8
0
Excellent! This is just the info I was looking for. Thanks Mark!
 

MIKX

macrumors 68000
Dec 16, 2004
1,815
691
Japan
The R9 280 X has two power sockets.
BOTH must be powered.

For the GPU 8 pin socket use

2 X Mini 6 pin to 1 x 8 pin
US$7.95 at Amazon

TWO mini 6 pin to ONE 8 pin GPU cable.jpg

For the GPU 6 pin socket

Remove TWO hard drives from the SATA bays - re-connect them in the upper DVD Drive cage.

Buy this cable ( TWO x SATA to one x 6 pin.)
US$7.99 ( two pack; you only need one cable
TWO SATA to ONE 6 pin.jpg

NOTE : You will have to "SNIP OFF" one of the locking lugs on each of the SATA cables.
SATA cable snipped.jpg



I also recommend putting a sticker on top of each to facilitate correct orientation for insertion into the cMP SATA sockets.
TWO SATA to ONE 6 pin WITH stickers.jpg

Whenever my cMPs sidecover is removed, I always givemy SATA cables a finger nudge to ensure that they are firmly inserted.
 

ava10

macrumors newbie
Original poster
Mar 2, 2020
8
0
The R9 280 X has two power sockets.
BOTH must be powered.

For the GPU 8 pin socket use

2 X Mini 6 pin to 1 x 8 pin
US$7.95 at Amazon

There are two 8 pin sockets on the card. Is it ok to use just one of the 8 pin connection?
 
Last edited by a moderator:

MarkC426

macrumors 68040
May 14, 2008
3,700
2,097
UK
There are two 8 pin sockets on the card. Is it ok to use just one of the 8 pin connection?
Ideally you would be better with a Pulse RX... card.
The RX560 has 4gb and needs no additional power at all (number 15 in the link).
Even the RX580 only has one 8 pin, which is powered by the two mini 6 on the motherboard.

Most people who are looking for all that extra power are trying really ‘meaty’ cards.
You shouldn’t need all that power for a 3gb card.
 
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MIKX

macrumors 68000
Dec 16, 2004
1,815
691
Japan
There are two 8 pin sockets on the card. Is it ok to use just one of the 8 pin connection?
No, if AMD put 2 power sockets on the card then one can safely assume that they want BOTH to be powered.

READ POST#4

You can insert the 6 pin ( 2 x SATA cable ) into the RIGHT SIDE of the OTHER R9 280X's 8 pin socket.


( This pic is just an example )

 6 pin to RIGHT SIDE of 8 pin socket.png




If you are worried about removing two HDDs / SSDs from the SATA bays. . you can remove your DVD Drive and install two HDDs / SSDs in the DVD drive cage, they will fit and there should be spare mounting screws in the DVD drive cage.
( I now use an external ASUS DVD drive )

To reiterate . .. BOTH of your R9 280X's 8 pin sockets MUST be powered.
 
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venonm

macrumors newbie
Jan 25, 2016
6
4
You can directly use 2 power cable to the board:
1x 6 minipin to 8 pin
1x 6 minipin to 6 pin

But both power connector on the card must be powered.
 

tsialex

Contributor
Jun 13, 2016
13,455
13,602
You can directly use 2 power cable to the board:
1x 6 minipin to 8 pin
1x 6 minipin to 6 pin

But both power connector on the card must be powered.
A 8-pin PCIe connector signals to the GPU that it can draw up to 150W.

Mac Pro mini-PCIe 6-pin is rated to 75W with the emergency power cut-out by the SMC at around 120W. So, you can't use just one mini-PCIe 6-pin to connect to a 8-pin PCIe GPU input.

While several people successfully draw more power from the mini-PCIe AUX connectors, it's not a god idea to use anything near to the power cut-out.

Around 90W, ok, while 110W+ is asking for a replacement backplane in the near future.
 

venonm

macrumors newbie
Jan 25, 2016
6
4
A 8-pin PCIe connector signals to the GPU that it can draw up to 150W.

Mac Pro mini-PCIe 6-pin is rated to 75W with the emergency power cut-out by the SMC at around 120W. So, you can't use just one mini-PCIe 6-pin to connect to a 8-pin PCIe GPU input.

While several people successfully draw more power from the mini-PCIe AUX connectors, it's not a god idea to use anything near to the power cut-out.

Around 90W, ok, while 110W+ is asking for a replacement backplane in the near future.

I know, but there is no problem with 280x, it always balances the consumption between both connectors.
The 280X is far from the maximum supported consumption.
It is totally safe to do it this way.
 

MIKX

macrumors 68000
Dec 16, 2004
1,815
691
Japan
I know, but there is no problem with 280x, it always balances the consumption between both connectors.
The 280X is far from the maximum supported consumption.
It is totally safe to do it this way.
I 100% disagree.

EDIT
Read Post #4 in this thread. = the "SAFEST & easiest" way to power any . . .
. . . . R9289/R9280X HD7950/ HD 7970.

Please do not post information that may damage, disable or cause CMP shutdowns.
 
Last edited:

h9826790

macrumors P6
Apr 3, 2014
16,656
8,587
Hong Kong
I know, but there is no problem with 280x, it always balances the consumption between both connectors.
The 280X is far from the maximum supported consumption.
It is totally safe to do it this way.
May be your card does that, but definitely NOT all 280X always balance the power draw between connectors.

In fact, from memory, the very first "bridge" power balancing method (on cMP) was developed on a 280X to avoid hard shutdown (which simply solder a very short cable between the 6 and 8pin on the graphic card's PCB).
 
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