MP 1,1-5,1 Undoing a flashed firmware

[jngphoto]

I flashed my 2009 MacPro to 5.1 to run Mojave. Now I want to undo it and run Snow Leopard.

I have a Snow Leopard boot drive. Can I take out the Mojave drive and replace it with the Snow Leopard drive?

 

[chabig]

It’s not possible to roll back firmware on Intel Macs. Maybe Snow Leopard will run with the updated firmware. Have you tried it?

When to revive or restore in DFU mode

When should you put your Mac into DFU mode, hook it up to another Mac running Configurator, and revive or restore it?

eclecticlight.co

 

[reader50]

Snow Leopard is not affected by the later firmware. Use it as normal.

 

[Borowski]

Snow Leopard 10.6 is fully supported from initial version on Mac Pro 5.1.

Or you're meaning Leopard (10.5)? It has no support for Mac Pro 5.1, those machines were delivered with Leopard.
Anyway, a firmware downgrade is only possible by manually flashing a reconstructed firmware.

 

[VaZ]

You can always click the Downgrade button on the tool you used if you really need to go back to 4,1

 

[tsialex]

You can always click the Downgrade button on the tool you used if you really need to go back to 4,1

This is incorrect, back then firmware downgrades were only possible if you still have MP51.07F.B03. Probably no one at all have this BootROM version anymore.

Once you updated to anything else, bye bye. OP most probably already have one of the Mojave firmwares, since he is running Mojave.

Anyway, you don't need to downgrade to run Snow Leopard.

 

[Tratkazir_the_1st]

Firmware Restoration CD 1.8 - Apple Support

The Firmware Restoration CD is used to restore the firmware of an Intel-based Macintosh computer.

support.apple.com

M.B. this? (Read twice before experimenting )

 

[tsialex]

Firmware Restoration CD 1.8 - Apple Support

The Firmware Restoration CD is used to restore the firmware of an Intel-based Macintosh computer.

support.apple.com

M.B. this? (Read twice before experimenting )

Only possible if you still have MP51.07F.B03…