Will NEW Mac Pro 5,1 BootROM firmware work with OLD OSX?

[cinealta]

I have a 2012 cMP 5,1 3.33 6-core with original 5770 GPU. Essentially I would like to try upgrading to Mojave (on a fresh boot SSD) but keep an older boot SSD, with an older OSX (eg Sierra or El Capitan), to use old software. I've bought a Sapphire Radeon RX580 Pulse 8Gb GPU to use with the Mojave boot SSD.

1) If I update the firmware to MP51.0089.B00 (and subsequently 138.0.0.0.0), can I still use an older OSX eg El Capitan or Sierra? Or am I permanently forced, on this cMP, to use Mojave from now on?

2) Where exactly is the new firmware written to, the CPU? Can I roll back to an older BootROM firmware if i have problems? If yes, how do I backup my older BootROM firmware or where can I download older versions?

Thank you.

 

[crjackson2134]

I have a 2012 cMP 5,1 3.33 6-core with original 5770 GPU. Essentially I would like to try upgrading to Mojave (on a fresh boot SSD) but keep an older boot SSD, with an older OSX (eg Sierra or El Capitan), to use old software. I've bought a Sapphire Radeon RX580 Pulse 8Gb GPU to use with the Mojave boot SSD.

1) If I update the firmware to MP51.0089.B00 (and subsequently 138.0.0.0.0), can I still use an older OSX eg El Capitan or Sierra? Or am I permanently forced, on this cMP, to use Mojave from now on?

2) Where exactly is the new firmware written to, the CPU? Can I roll back to an older BootROM firmware if i have problems? If yes, how do I backup my older BootROM firmware or where can I download older versions?

Thank you.

Older versions of OS X won't be obsoleted by way of the firmware upgrade. You're fine there.

You need to do some reading. No need to repost all the information that's already pervasive in this forum about firmware upgrading. Do some homework.

You might start here, and also look for other related threads, until you get it...

https://forums.macrumors.com/threads/mp5-1-what-you-have-to-do-to-upgrade-to-mojave.2142418/

https://forums.macrumors.com/threads/mp5-1-mojave-bootrom-138-0-0-0-0-139-0-0-0-0.2132317/

 

[tsialex]

I have a 2012 cMP 5,1 3.33 6-core with original 5770 GPU. Essentially I would like to try upgrading to Mojave (on a fresh boot SSD) but keep an older boot SSD, with an older OSX (eg Sierra or El Capitan), to use old software. I've bought a Sapphire Radeon RX580 Pulse 8Gb GPU to use with the Mojave boot SSD.

1) If I update the firmware to MP51.0089.B00 (and subsequently 138.0.0.0.0), can I still use an older OSX eg El Capitan or Sierra? Or am I permanently forced, on this cMP, to use Mojave from now on?

2) Where exactly is the new firmware written to, the CPU? Can I roll back to an older BootROM firmware if i have problems? If yes, how do I backup my older BootROM firmware or where can I download older versions?

Thank you.

1) With 13[8,9].0.0.0.0 You can boot any macOS version supported by your Mac Pro. You can boot even 10.6.8, unsupported by 2012 MP, but you will have some trouble with the serial number if you try 10.6.8.

2) BootROM is stored on a 8-pin SOIC SPI flash memory on the backplane (logic board). Apple designed it as a upgrade only, not to downgrade it with Apple tools. You can backup your current one (dump it) using dosdude1 ROMTool. You can download older versions, but is useless to you as they can’t be used to downgrade. Apple ones are generic without any hardware ids and only can be used for upgrading your current one.

 

[Auggie]

Although I was able to boot to older versions (I have 10.8.5, 10.10.5, and 10.12.6) I did experience a significant problem that I suspected had to do with the newer firmware with one of them but don't recall the nature or the severity.

Since I rarely boot into them, it wasn't a showstopper for me and I carried on, but if I need to boot into an older OS again, I will try recreating the issue and report back.

 

[minifridge1138]

My 4,1 -> 5,1 is updated to Mojave and has the latest firmware.

I just booted 10.6.8 with (almost) no trouble. I don't think it liked my HD 7950, but probably would have been happy with the HD 5870 I used back in the Snow Leopard days. I only had video out of the mDP, not the D-DVI port. It said my memory was correctly installed and could not initialize my APFS drive (big surprise).

I also booted an old Windows XP partition I have laying around. It worked, detected 7950, and auto-installed all of the needed drivers. I'm actually really impressed.

So my experience: if the older OS would be happy with your hardware, then it will still be happy with the newest firmware.

 

[cinealta]

1) With 13[8,9].0.0.0.0 You can boot any macOS version supported by your Mac Pro. You can boot even 10.6.8, unsupported by 2012 MP, but you will have some trouble with the serial number if you try 10.6.8.

2) BootROM is stored on a 8-pin SOIC SPI flash memory on the backplane (logic board). Apple designed it as a upgrade only, not to downgrade it with Apple tools. You can backup your current one (dump it) using dosdude1 ROMTool. You can download older versions, but is useless to you as they can’t be used to downgrade. Apple ones are generic without any hardware ids and only can be used for upgrading your current one.

Thank you!