Flashed 4,1>5,1 says a firmware update is required

[NorCalLights]

Hey y'all,
On my 4,1 flashed to 5,1 and I've been happily running High Sierra for many months. Today, I need to instal a fresh copy of High Sierra onto an SSD I've added to a PCI Slot. I downloaded the installer from the App Store, and now it's telling me "To install macOS High Sierra, a firmware update is required."

I'm afraid to install any firmware because I don't want to mess up the 5,1 firmware I have loaded. Any idea why it would be telling me this? System Information is reporting a Boot ROM Version of MP51.0084.B00

Thanks

 

[h9826790]

Hey y'all,
On my 4,1 flashed to 5,1 and I've been happily running High Sierra for many months. Today, I need to instal a fresh copy of High Sierra onto an SSD I've added to a PCI Slot. I downloaded the installer from the App Store, and now it's telling me "To install macOS High Sierra, a firmware update is required."

I'm afraid to install any firmware because I don't want to mess up the 5,1 firmware I have loaded. Any idea why it would be telling me this? System Information is reporting a Boot ROM Version of MP51.0084.B00

Thanks

The latest 10.13.6 full installer has a 0089.B00 firmware in there for 5,1. If you want to run it, you should perform the firmware update first.

If you don't like it, you can rename the firmware file inside the installer to a version that lower than your current version.

e.g. make it 0083.B00, then no firmware upgrade request will pop up.

 

[bookemdano]

You'll be fine (so long as you have the stock GPU installed, or another one that shows you the Apple logo screen when you boot up).

It will update your firmware to MP51.0089.B00, which has a bunch of microcode fixes in it. It will not revert you to 4,1, so you're safe there

 

[NorCalLights]

Thank you so much for such a quick reply!

 

[crjackson2134]

Hey y'all,
On my 4,1 flashed to 5,1 and I've been happily running High Sierra for many months. Today, I need to instal a fresh copy of High Sierra onto an SSD I've added to a PCI Slot. I downloaded the installer from the App Store, and now it's telling me "To install macOS High Sierra, a firmware update is required."

I'm afraid to install any firmware because I don't want to mess up the 5,1 firmware I have loaded. Any idea why it would be telling me this? System Information is reporting a Boot ROM Version of MP51.0084.B00

Thanks

I recommend you do the firmware upgrade. It's an ACTUAL upgrade. You need the microcode updates to mitigate vulnerabilities.

 

[NorCalLights]

Installed and everything went great.
Thanks, all.