I had an old Mac Pro 1,1 lying around and happened to have two 6870's, so I decided to Crossfire them and see how it performed. And yes, this only works in windows. In OS X, the xfire bridge is ignored.
So far the results have been impressive: L4D2 is running maxed out perfectly. I haven't tried much else.
There are some issues, however, that you definitely need to be aware of...
POWER: I recently wrote this tutorial on how to rig a 2nd PSU. You WILL need one. Just make sure you have one of the motherboard's 6 pin plugs in each of the cards (the other plug on each card should be externally powered). This seems to be only true with the Mac Pro 1,1, my MP 5,1 had no such issue. The Mac Pro 1,1 needs both cards to have at least one of the plugs to have power immediately. If you have an external PSU that is not providing power when the internal (main) PSU is off, the card you are powering externally will not be detected because the initialization process will occur prior to the circuits being powered. It becomes necessary therefore to have the external and internal PSU to each be hooked up to both cards. This is not a big deal, just make sure the motherboard's two 6 pin plugs are each plugged into one of the ports on each card. Other other port can be powered externally. After that, everything worked fine. This is not a big deal but turned out to be a big headache. Note that my MP 5,1 did NOT have this issue.
PCIe SPEED CONFIGURATION: When you first boot the computer into OS X, a program should automatically open asking how you want the PCIe speed to be configured. In Newer Mac Pros, you can do 16x in both ports 1 and 2!! For my old Mac Pro 1,1, I can only do 8x in those ports
. If the program doesn't open, you can find it by going into the finder's "GO" menu, click "go to folder" and type "/System/Library/Core Services", then find "expansion slot utility". Here's Apple's article on that.
BOOT SCREENS: Not on the MP 1,1, you have to use a "helper" card for those. The helper card will not enable boot screens on the 6870, but you can plug a monitor into it and use it in case of emergencies. For newer macs with EFI 64, you can flash the 6870 and the boot screens work fine. However, you don't need boot screens to boot (they are just really helpful if something bad happens or if you want to use the boot selector).
COOLING: You NEED to turn up the PCIe bay fan to at least 2000 RPM when running crossfire in Windows.
If you do not, you could get a BSOD from overheating even while installing the catalyst drivers !!
To do this in windows, download the program MacFan. Right click on the proper build (use MacFan64 if you have 64 bit windows, use the other if you don't), and click "RUN AS ADMINISTRATOR". After that, I would advise creating a batch file to adjust the fan speed.
Here is a video on how to use this program, but I wrote my own how-to below that's probably not as good.
If you run it from start menu search "cmd", you can see the current fan speed. To set the fan speed, you have to run the program and add each target fan speed, in order, separated by spaces afterwards, so I found out my PCIe fan was the 2nd fan in the list I did this by cranking up the RPM and seeing which one spun (yep, trial and error). I wanted the PCIe fan to be 2000RPM and the other 3 fans to be 1200. This is how I set that
[IN QUOTES] "C:\[path\to\MacFan\Program.exe]" 1200 2000 1200 1200
It gave me an error saying the 4th fan speed could not be set. Don't care, that's fine. A few seconds after executing this command, you should hear the PCIe fan spin up. Get used to the noise
Here's how you make that into a batch file:
1. Download MacFan and run it as Administrator one time as above (right click on it)
2. Test the program as above and see which fans you want to run at which RPM. I basically ran the program once and doubled the RPMs I was seeing.
3. [Create a batch file in the startup items]
When you start Windows, you should hear the PCIe fan spin up. If you don't, you or I did something wrong.
WARNING: Supposedly the fan speeds go back to default when you go in and out of "standby" in windows. You will therefore need to re-run that batch file.
Have fun !
So far the results have been impressive: L4D2 is running maxed out perfectly. I haven't tried much else.
There are some issues, however, that you definitely need to be aware of...
POWER: I recently wrote this tutorial on how to rig a 2nd PSU. You WILL need one. Just make sure you have one of the motherboard's 6 pin plugs in each of the cards (the other plug on each card should be externally powered). This seems to be only true with the Mac Pro 1,1, my MP 5,1 had no such issue. The Mac Pro 1,1 needs both cards to have at least one of the plugs to have power immediately. If you have an external PSU that is not providing power when the internal (main) PSU is off, the card you are powering externally will not be detected because the initialization process will occur prior to the circuits being powered. It becomes necessary therefore to have the external and internal PSU to each be hooked up to both cards. This is not a big deal, just make sure the motherboard's two 6 pin plugs are each plugged into one of the ports on each card. Other other port can be powered externally. After that, everything worked fine. This is not a big deal but turned out to be a big headache. Note that my MP 5,1 did NOT have this issue.
PCIe SPEED CONFIGURATION: When you first boot the computer into OS X, a program should automatically open asking how you want the PCIe speed to be configured. In Newer Mac Pros, you can do 16x in both ports 1 and 2!! For my old Mac Pro 1,1, I can only do 8x in those ports
. If the program doesn't open, you can find it by going into the finder's "GO" menu, click "go to folder" and type "/System/Library/Core Services", then find "expansion slot utility". Here's Apple's article on that.BOOT SCREENS: Not on the MP 1,1, you have to use a "helper" card for those. The helper card will not enable boot screens on the 6870, but you can plug a monitor into it and use it in case of emergencies. For newer macs with EFI 64, you can flash the 6870 and the boot screens work fine. However, you don't need boot screens to boot (they are just really helpful if something bad happens or if you want to use the boot selector).
COOLING: You NEED to turn up the PCIe bay fan to at least 2000 RPM when running crossfire in Windows.
If you do not, you could get a BSOD from overheating even while installing the catalyst drivers !!
To do this in windows, download the program MacFan. Right click on the proper build (use MacFan64 if you have 64 bit windows, use the other if you don't), and click "RUN AS ADMINISTRATOR". After that, I would advise creating a batch file to adjust the fan speed.
Here is a video on how to use this program, but I wrote my own how-to below that's probably not as good.
If you run it from start menu search "cmd", you can see the current fan speed. To set the fan speed, you have to run the program and add each target fan speed, in order, separated by spaces afterwards, so I found out my PCIe fan was the 2nd fan in the list I did this by cranking up the RPM and seeing which one spun (yep, trial and error). I wanted the PCIe fan to be 2000RPM and the other 3 fans to be 1200. This is how I set that
[IN QUOTES] "C:\[path\to\MacFan\Program.exe]" 1200 2000 1200 1200
It gave me an error saying the 4th fan speed could not be set. Don't care, that's fine. A few seconds after executing this command, you should hear the PCIe fan spin up. Get used to the noise
Here's how you make that into a batch file:
1. Download MacFan and run it as Administrator one time as above (right click on it)
2. Test the program as above and see which fans you want to run at which RPM. I basically ran the program once and doubled the RPMs I was seeing.
3. [Create a batch file in the startup items]
- Go into start menu and right click on programs / startup
- Right click on "startup" and select "open/explore all users"
- Right click in the empty open folder and click "create new text file"
- [ you should be in notepad now]
- Go into file -> save as, click on the pull-down menu for file-type and click "all files"
- Save the file as fanstart.bat (or ihatewindows.bat or whatever, just make sure it's .bat ... PLease note that if you save as .txt it wont run
- The icon of the file you saved should look like a gear or something and not a regular text file--indicating it's an executable batch file
3. While editing the file in notepad, on the first line write "@echo off" (no quotes), on the second line do the following- Right click on "startup" and select "open/explore all users"
- Right click in the empty open folder and click "create new text file"
- [ you should be in notepad now]
- Go into file -> save as, click on the pull-down menu for file-type and click "all files"
- Save the file as fanstart.bat (or ihatewindows.bat or whatever, just make sure it's .bat ... PLease note that if you save as .txt it wont run
- The icon of the file you saved should look like a gear or something and not a regular text file--indicating it's an executable batch file
- [IN QUOTES] "C:\[path\to\MacFan\Program.exe]" 1200 2000 1200 1200
- ( Or whatever you want your fan speed to be)
- hit save
- ( Or whatever you want your fan speed to be)
- hit save
When you start Windows, you should hear the PCIe fan spin up. If you don't, you or I did something wrong.
WARNING: Supposedly the fan speeds go back to default when you go in and out of "standby" in windows. You will therefore need to re-run that batch file.
Have fun !
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