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ATI 4850 Crossfire - Windows. Not OSX

S

swiss tony

macrumors newbie
Original poster
Jun 11, 2008
27
0
Would this work?
Obviously only under windows, i could find on google any macpros with CrossFire. Anyone here managed it.

Thanks in advance.
 
As Crossfire isn't limited to any particular motherboard compared to SLI, it'll work. However, don't expect to be using either of them in OS X.
 
I see. Why not just build yourself a PC then? It'd be cheaper... your money to spend, obviously, just doesn't make much sense to buy a Mac Pro just to run Windows all the time.
 
well ive been doing my research, looking for a 8 core machine for rendering, turns out that mac sells the cheapest esp with a 20% educational discount, the machine is basicly a PC so thats why. Saves cash, expandable, better than skulltrail (buggy crud) looks ok comes with a warranty.
 
Be sure to check the power requirements of your cards. I don't think you can put two 4870 into the Mac Pro. At least not with out pulling some more power from somewhere other than the motherboard. I know you are looking at the 4850s, but they may have the same issue, 160 watts.
 
pyramid6 said:
Be sure to check the power requirements of your cards. I don't think you can put two 4870 into the Mac Pro. At least not with out pulling some more power from somewhere other than the motherboard. I know you are looking at the 4850s, but they may have the same issue, 160 watts.
Click to expand...
Just feed directly from the power supply instead of the motherboard passthrough..
 
I'll guess i'll try it out, i'm sure a server PSU can hack it. Ive always been confused by the 300w PCI comment, as it doesnt specificly mention the capacity of the pci-e connectors, they must run to specification, it seems that if a card has one connector that it could not exceed the spec for the Wattage that it could provide, and by that logic the mac pro mobo could not be underspecified. The 4870 requires 2 pci-e power points, so obviously the 4850 would be much better CrossFire, and is easier on the wallet.

I like the mac pro design except the handles, its certainly a step up from dell and most computer manufacturers designs. Alienware - dell - what are they thinking. Maybe just the architect in me talking!

I'm interested to see what happens with Xfire!
 
meh no worries good that these things are bought up, beats the 'ol mac v windows trolling!
 
swiss tony said:
I'll guess i'll try it out, i'm sure a server PSU can hack it. Ive always been confused by the 300w PCI comment, as it doesnt specificly mention the capacity of the pci-e connectors, they must run to specification, it seems that if a card has one connector that it could not exceed the spec for the Wattage that it could provide, and by that logic the mac pro mobo could not be underspecified. The 4870 requires 2 pci-e power points, so obviously the 4850 would be much better CrossFire, and is easier on the wallet.

I like the mac pro design except the handles, its certainly a step up from dell and most computer manufacturers designs. Alienware - dell - what are they thinking. Maybe just the architect in me talking!

I'm interested to see what happens with Xfire!
Click to expand...

It's quite simple actually.

Every PCI-Express slot can supply 75 Watt of power. 4 x 75 = 300 Watt. That is the amount of power the Mac Pro can supply through the PCI-Express slots.

However, you are not limited (other than power supply specifications) when it comes from drawing power directly from the power supply with a power cable.
 
Mac OS

Has any one tried the 4870 PC card w/the mac video card in the other slot.(I'm referring to Mac Pro 2008 with 2 PCI-E 2.0 16x slots) Will the Mac boot to the mac video card under OS X or Kernal panic cause of the foreign card? Please no guesses. Has anyone actually done this?
 
Pressure said:
It's quite simple actually.

Every PCI-Express slot can supply 75 Watt of power. 4 x 75 = 300 Watt. That is the amount of power the Mac Pro can supply through the PCI-Express slots.

However, you are not limited (other than power supply specifications) when it comes from drawing power directly from the power supply with a power cable.
Click to expand...

I'm still confused. :confused: Every post I read about adding super fast video cards there's always a caveat that you cannot exceed the 300 watt limit. So if you have a card that pulls 190 watts you cannot install two of them. Now I know that the cards have an auxiliary cable that plugs into the MB power connector so why is there a 300 watt limit? Please enlighten me.
Thanks
 
Siron said:
I'm still confused. :confused: Every post I read about adding super fast video cards there's always a caveat that you cannot exceed the 300 watt limit. So if you have a card that pulls 190 watts you cannot install two of them. Now I know that the cards have an auxiliary cable that plugs into the MB power connector so why is there a 300 watt limit? Please enlighten me.
Thanks
Click to expand...
It's because that's the max that the PCI slots can supply. The motherboard can supply more through the two six-pin slots, but the PCI slots are limited to 300 watts.
 
Mackilroy said:
I see. Why not just build yourself a PC then? It'd be cheaper... your money to spend, obviously, just doesn't make much sense to buy a Mac Pro just to run Windows all the time.
Click to expand...

It's always been cheaper to get a mac pro than the same stuff in the PC world.

That's why I bought the mac pro in the first place.. PC would've been 20% more!

Weird, I know... maybe even a first for Apple
 
Would a 4850 and the new Mac/PC 3870 connected with Crossfire work okay or would pairing it with the 3870 drag performance down to what two 3870s would provide (at a cheaper price)?
 
Siron said:
Would a 4850 and the new Mac/PC 3870 connected with Crossfire work okay or would pairing it with the 3870 drag performance down to what two 3870s would provide (at a cheaper price)?
Click to expand...

As far as I know this combination is not officially supported, but works in many cases.
Performance would certainly be better than two 3870. But I think that the performance gain will not be very big over a single 4850 because specially in high resolutions/AA settings the 4850 alone can be twice as fast as the 3870
 
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