Docs: Add non-flashed GPU information

Authored-By: @Jazzzny

docs/BOOT.md

@@ -8,6 +8,50 @@ Reboot machine while holding `Option` to select the EFI Boot entry with the Open
 
 ![](../images/efi-boot.png)
 
+::: details Note for Mac Pros/Xserves/iMacs with unflashed GPUs
+
+(Adapted from the [OpenCore on the Mac Pro guide](https://forums.macrumors.com/threads/opencore-on-the-mac-pro.2207814/))
+
+For Mac Pro, Xserve and, iMac users with non-flashed GPUs, you can still easily boot OpenCore and view the entire boot process.
+
+Firstly, open the Terminal and run the following command:
+```sh
+sudo nvram "recovery-boot-mode=unused" && sudo reboot recovery
+```
+This will make your machine reboot into the Recovery Environment. Alternatively, holding Command + R when your machine is starting up will also let you enter the Recovery.
+
+Secondly, open the Recovery Environment's Terminal (Menu bar > Utilities > Terminal).
+
+Now you'll want to get a list of drive identifiers. To do so, run the following command:
+```sh
+diskutil list
+```
+The command should produce a list of drives installed in your system:
+![](../images/Unflashed-Boot-1.png)
+
+Keep track of the drive with the OCLP install. You will need the drive identifer for later.
+
+Now you'll want to mount the EFI partition (where OCLP is installed, though may differ if you've installed OCLP to a FAT-32 volume).
+
+Run the following command (Replace X with the drive number):
+```sh
+diskutil mount diskXs1
+```
+![](../images/Unflashed-Boot-2.png)
+If everything is correct, the EFI partion should be mounted.
+
+Now you'll want to use the bless command to set the default boot device:
+```sh
+bless --mount /Volumes/EFI --setBoot --file /Volumes/EFI/System/Library/CoreServices/boot.efi
+```
+Once the command is run, it should produce no output.
+![](../images/Unflashed-Boot-3.png)
+
+If the command produces an output, ensure that you've typed it in correctly.
+
+Now you can reboot your machine. OCLP is now the default boot option!
+:::
+
 Now that you've loaded OpenCore, now select Install macOS:
 
 * This will be the OpenCore Picker
@@ -23,7 +67,7 @@ If your Mac is looping back into the beginning of the setup after the first rebo
 ![](../images/oclp-stuck-firstreboot.png)
 
 
-::: warning 
+::: warning
 
 **MacBookPro11,3 Note**: When booting macOS Monterey, you'll need to boot into safe mode if acceleration patches are not installed yet. [Otherwise you'll hit a black screen due to missing NVIDIA drivers.](https://github.com/dortania/OpenCore-Legacy-Patcher/issues/522) Safe Mode can be entered by holding Shift+Enter when selecting macOS Monterey in OCLP's Boot Menu.