Installing 2 Radeon HD5870 cards in a Mac Pro 2010

par linathael - 27/09/2010

Procedure to installi two cards and evaluation of performance levels on Mac OS X and Windows (including Crossfire mode)

Installation

First step: is the Mac Pro PSU able to deliver enough power for a second HD5870 graphics card?
With at least 1,000W or even 1,400W in the Mac Pro 2008, it should be enough.

However, let’s get the ultimate Mac Pro and calculate its max power consumption:

2 Xeons X5670 : 2 x 95 W = 190 W
2 R5870 : 2 x 160 W = 320 W
5 x 2 TB WD Caviar Black (4 HD bays + optical) = 5 x 12 W = 60 W
8 x 8GB RAM DDR = 8 x 10 W = 80 W

Giving a total of 650W. So, 350W is still available to power the motherboard and other components, and it should be more than enough; however you never know in advance how limits may have been set for each power cable.

Second step: where can we get 2 PCIe 6-pin power cables for the second card?
Let’s look at the way the cards are installed. Indeed, the second card will have a rather bad air flow input as slots 1 and 2 in the Mac Pro leave only a few millimeters of space between the cards. Luckily, the Radeon HD5870 Mac Edition is based on the ATI/AMD reference design for its cooling system, so it is efficient even though it can be a bit noisy, so with the rev2 design of the XFX card, it leaves enough space for both cards to get enough fresh air to cool their respective GPUs. So, we installed the Mac Edition card below the XFX card.

Last but not least, to limit the load on the SATA power line, we will plug 1 PCIe 6-pin power cable into each card. With such a setup, both cards will be powered by both the motherboard and the SATA port.

Hereafter is a photo illustrating the proper setup for obtaining a stable configuration:

On the right is the Crossfire bridge, linking both cards. It is recommended to attach the SATA-Molex adaptor to the HD tray to avoid any unplugging that could happen following an accidental shock on the case. It can also be beneficial to optimize as much as possible the way cables are installed in order to increase as much as possible the air flow.

It is now time to close the enclosure of the Mac, and get ready to unplug the power cord to quickly shut down everything in case of problems. You can then press the power button… and get ready!