Here is the standard procedure for flashing ATI cards in PC if you have a suitable Mac ROM for your card.

• Download the Mac ROM intended for your PC ATI card from The Mac Elite, here :

• First of all you will have to make a DOS bootable disk (or USB flash disk if your PC supports booting from USB) and copy over atiflash.exe, along with the BIOS you choose to use.
Latest ATIFLASH program can be found at http://www.techpowerup.com/, you will also find there a huge ATI ROM collection for PC card (and even some Mac ATI ROMs)
Latest ATIFLASH (3.10 and above) supports flashing 128KB ROM if your card has a 128KB rom chip.

• Flashing with ATIFLASH 3.10 and above:
After you created the bootable disk, restart your PC with the boot disk. At the command prompt, type the following and begin your flash process.

Buy AMD Radeon HD 7950 3GB GDDR5 for Apple MAC Pro PCIe x16 Mini-DisplayPort HDMI DVI GPU Graphics Video Card 4K & 5K. Included Components, —, installation CD, manual, Graphics Card, quick install guide, driver cd, —. In that thread, post #1 is the link to the script you need to run on OS X to take the ROM file you dump from your card and put it together with the EFI portion so you get the boot screen on a Mac Pro.

a:>atiflash -i [Enter]

Will check the system for ATI cards installed. If there are several, they will be numbered, counting from '0'. Check out whichh is the card to be flashed.

a:>atiflash -s backup.rom [Enter]

Standard back-up (saves BIOS to Floppy/current directory)
(note : 'a:>' might be a different letter if you're booting from anything else than a floppy disk. USB 'Pen Drive' will work as standard Hard Drive and command prompt will probably look like 'c:>')

How to make a bootable usb for mac os x mavericks dmg free. Set the Format type to Mac OS Extended (Journaled.) Click on the Apply button and wait for the Done button to activate. When it does click on it. Quit Disk Utility. Create Installer. Open the Terminal in the Utilities' folder. Choose the appropriate command line (in red) depending upon what OS X installer you want. After creating the bootable installer, follow these steps to use it: Plug the bootable installer into a compatible Mac. Use Startup Manager or Startup Disk preferences to select the bootable installer as the startup disk, then start up from it. Your Mac will start up to macOS Recovery. Follow these steps: Using a Mac with at least OS X 10.6.8 installed, access the Mac App Store and download the Mavericks (10.9) app installer. Insert the USB drive into the Mac and launch Disk Utility. Click on the USB drive from the left-hand menu and select the Partition tab.

a>:atiflash -p 0 mac.rom -f [Enter]

-p is switch to program the rom.
0 (zero) is the adapter number, if there is only one card installed. If you have 2 ATI cards, check first which adapter number is the card you want to flash (see above).
mac.rom is the Mac ROM file you want to flash to your card.
-f is the switch to allow forced flash for different ROM revision or if there's a DeviceID mismatch between PC ROM and Mac ROM

If everything is fine, you should get a message telling the flash process went fine.
If you get an error message, flash your card back to PC ROM to avoid being stuck on PC reboot with a misflashed ATI card.

This flashing procedure should work with almost every ATI card which has a known working mac rom (original or modified, full 128KB or reduced to 64KB)

Check ATIFLASH DOS command line help to get full switches and options list as it depends on the version of the ATIFLASH program you're using.
FLASHROM DOS command line program also has equivalent features. However, it is not supposed to work with 128KB Mac ROMs.

If a 9500 or 9700 does not work on the Mac, check whether it requires separate power supply (PC-floppy-disk-power-connector opposite side to the VGA plug).

This article applies only to video cards that originally shipped with a specified Mac Pro or were offered as an upgrade kit by Apple. Similar cards that were not provided by Apple may have compatibility issues and you should work with the vendor of that card to confirm compatibility.

Mac Pro (2019)

Learn more about cards you can install in Mac Pro (2019) and how to install PCIe cards in your Mac Pro (2019).

Mac Pro (Late 2013)

• Dual AMD FirePro D300
• Dual AMD FirePro D500
• Dual AMD FirePro D700

Mac Pro (Mid 2010) and Mac Pro (Mid 2012)

• ATI Radeon HD 5770
• ATI Radeon HD 5870
  Learn about graphics cards supported in macOS 10.14 Mojave on Mac Pro (2010) and Mac Pro (Mid 2012).

Mac Pro (Early 2009)

• NVIDIA GeForce GT 120
• ATI Radeon HD 4870
  
• ATI Radeon HD 5870, offered as an upgrade kit
  The Radeon HD 5870 card requires Mac OS X 10.6.4 or later and the use of both auxiliary power connections.

Mac Pro (Early 2008)

• ATI Radeon HD 2600 XT
• NVIDIA GeForce 8800 GT (part number 630-9191 or 630-9897)*
• NVIDIA Quadro FX 5600
• ATI Radeon HD 4870, offered as an upgrade kit
  The Radeon HD 4870 card requires Mac OS X 10.5.7 or later.

Mac Pro (Original)

• NVIDIA GeForce 7300 GT
• ATI Radeon X1900 XT
• NVIDIA Quadro FX 4500 (part number 630-7532 or 630-7895)*
• NVIDIA GeForce 8800 GT (part number 630-9492), offered as an upgrade kit.*
  The NVIDIA GeForce 8800 GT card requires Mac OS X 10.5.2 or later with the Leopard Graphics Update 1.0 or the computer may not start up properly.

* To identify a graphics card part number, check the label on the back of the card.