2 HD 5870s in 2010 MacPro

I already have an auxiliary PSU that goes into the empty optical drive slot.

What stopped me so far, is that I cannot work out if Mac Pro 2010 has two PCIe x16 slots. If the Mac Pro doesn't support two PCIe x16 slots and drops speeds to x8 when two GPUs are plugged into mobo then it's a waste of time and effort.

Does anyone know if Mac Pro 2010 has two PCIe x16 or not?

when you open your Mac's side door you will see the video card installed and 3 empty PSI slots above it (if you have nothing added to ones).

these 3 slots are :
1 x PCI Express 2.0 x16 slot
2 x PCI Express 2.0 x4 slots

So, if I have two GPUs plugged in they will both be x16 and not two times x8 then?

This is tedious if not at all possible.. since the Power supply is only 1000(987 watts).. Personally, I wouldn't bother with it.. but I am not an extreme gamer.. Wait a second.. I thought the Mac Pro isn't designed for HARD CORE Gaming??

then again, I am ANTI-GAMING on a mac 🙂

You are wrong.. there are two 16x 2.0 PCIe slots and two 4x 2.0 PCIe slots..

romko23 wrote:
since the Power supply is only 1000(987 watts)..

Actually, that's enough to power two large GPU -- my other computer is a PC with 1200W PSU and it runs three very power hungry nVidia GTX280 in SLI, plus four WD Velociraptor hard drives.

Besides the original poster said he was considering using a supplementary PSU, and I have one too. Rather than overstressing the PSU it appears lack of cable connectivity is the problem.

then again, I am ANTI-GAMING on a mac 🙂

So why did you bother posting in this thread? That's not very helpful. Plus, why should you care what other people do with their Mac Pro?

Answer
Apple has this page http://support.apple.com/kb/HT2838 which explains that Mac Pro (Original) and Mac Pro (8x) needed +Expansion Slot Utility+ to manage the PCIe lanes; but that Mac Pro (Early 2008) and Mac Pro (Early 2009) the slots are permanently set where Slots 1 and 2 are both x16 revision 2.0 slots.

Unfortunately this support document doesn't cover Mac Pro (Mid 2010) but I imagine it will be the same, which is good news as it means both PCIe x16 should remain at x16 if both slots are filled (and not drop to x8 as they did in old hardware).

I just think Windows has you beat with games.. Sorry, but the Mac Pro will never ever(so long as Steve is leader), will have the firepower of a custom gaming PC.. Sorry.. You can't SLI in bootcamp, though you can crossfire in Bootcamp.. OS X Will never support these features because to the die hards for the mac pro, it was never designed to replace a custom gaming pc.

Even the imac is weaker compared to a gaming pc.

You can slot 2 16x cards in any of the 4 PCIe. The remaining bandwidth is left at a reduced speed for the last 2 slots based on PSU load specs (A utility is available that lets you know where and how your bandwidth is allocated). I have seen others use a Y splitter on their PSU to get juice to 2nd card. It appeared to be stable. This was not crossfire but one ATI gpu for display and one Nvidia gpu for cuda/ OpenCL.

BoyHowdyDoo wrote:
You can slot 2 16x cards in any of the 4 PCIe. The remaining bandwidth is left at a reduced speed for the last 2 slots based on PSU load specs (A utility is available that lets you know where and how your bandwidth is allocated).

If it runs two 16x at full 16x then fantastic, although after some research I discovered that two 16x cards running at 8x (as on older PCIe systems) is only 10-15% slower than full speed.

I have seen others use a Y splitter on their PSU to get juice to 2nd card. It appeared to be stable.

I've got three HD and two SSD drives in the box, really don't want to over stretch it ... and have a GPU power supply spare. 🙂

This was not crossfire but one ATI gpu for display and one Nvidia gpu for cuda/ OpenCL.

In Mac OSX and during work time I only need to use one card, the second 5870 card is purely for gaming at 2560x1600 in +Boot Camp+ after-hours.

According to Apple it is 2x16x slots at full power. They should not split to 8x each like a cheaper PC mobo. This is old but does state 2 full power 16x slots in the 2009's but they are slot specific. The new 2010's are not slot specific.
http://support.apple.com/kb/HT2838
You could just call Apple. The documentation does appear slightly misleading.

Have you found anymore information about this? I also would like to do a crossfire of two 5870 cards. Have you found anybody who has done it now that the 5870 is shipping via the apple store? Are you sure that you need another power supply? I read in a macrumors forum thread that this would be unnecessary.

Thanks,
Jake

Yes, you need another power supply.. although the power supply in the 09 and 10 is 980watts or 1000 watts, seems there is only one set of PCIe connectors on the board for only one 5870.. You would need a y-splitter and a smaller power supply - Personally, not worth it.. Better a gaming PC then a mac pro for heavy gaming..

Mac Pro was never designed for "HEAVY GAMING" = Want that? GOTO A PC.

Thank you for your reply romko23, I appreciate your info regarding the power supply. I do not appreciate, however, being chastised in a condescending tone for wanting to do my "heavy" gaming on my mac pro.

I "heavy" game on the Mac Pro. It is quieter than my PC's ever were. And everything is still tweak-able under Windows. Don't see what the problem is there. If you have to have serious power for OS X and you like to game, it is a great choice. If you just like to game than yes, it is a waste of money.

http://arstechnica.com/apple/reviews/2010/10/tri-screen-cpu-monitor-ars-reviews- the-12-core-2010-mac-pro.ars/2

They did it with just a Y-split no need for smaller extra power supply. A 1000 watt supply can do like 12 HDD's, Dual Quad Procs and Crossfile/ SLI at the same time no problem. There are few PSU's rated over that anyway.

I do not know anyone that has crossfired Apple's 5870's.
This guy did 2x4870's. So it should be similar.
http://www.flickr.com/photos/36197914@N08/sets/72157616169842077/
And thread for this to make sense.
http://forums.macrumors.com/showthread.php?t=665034&page=10

That should get you going. Don't believe the naysayers.

I have fitted two Radeon HD 5870 inside my 12-core Mac Pro (mid 2010).

I wasn't confident about the PSU and using Y-splitters as I've got two powerful CPUs as well as three large 10000-rpm HDD and a couple of large SSDs too, so I used an old GPU external power supply I had in a cupboard and run the cables in through to last PCI slot at the top.

Two Radeon HD 5870 work perfectly in Mac OSX, and in my Boot Camp I've got them linked with CrossFire ... 24-threads and two HD 5870 is a kick-*** games machine.

Next steps: run with Y-splitters and see what PSU can handle.