iMac 8,1 Catalina Patcher, Firmware Programming Mode

[markapplelover]

So I am trying to install Catalina Patcher on my mom's iMac early 2008 8,1 and to boot off of APFS (which I want for the software updates), I need to patch firmware. I see two options:

1. Under the Mojave Pacther page there is a mention of a firmware package but not sure if it is needed for my particular imac (see below)
   1. Important Note: If you have a machine that supports High Sierra natively, you MUST ensure you have the latest version of the system's BootROM installed if you want to boot from an APFS volume. If you have NOT previously installed High Sierra, you can download and install this package to install the latest BootROM version. When installing, ensure your system is plugged in to power, or the update will not be installed.
2. He also has a standalone APFS Rom Patcher but it wants me to enter the firmware programming mode but there are no lights to flash on my iMac and holding down the power button does nothing except booting regular (s far as I can tell)

So I'm stuck. Do I do step 1 and will this make step 2 not needed? Do I run step 2 with being in the firmware programming mode? I can do the rest as I have used the patcher elsewhere but stuck here

Or should I use high sierra patcher first update that hoping a firmware update will be installed then start over.

 

[Nguyen Duc Hieu]

I just share my own experience:
Example 1
iMac 24" early 2009 (iMac 9,1)
Original OS: OSX El Capitan
I removed the SSD, put it in an USB enclosure and partitioned it to APFS on another iMac 11,2 (mid 2010)
I then used the dosdude1 USB installer to install Catalina to the SSD, on the iMac 9,1.

Example 2
iMac 27" late 2009 (iMac 10,1)
Original OS: OSX Maverick
ROM version look updated, but I install High Sierra on the internal HDD anyway.
After that, I cloned the Catalina SSD in example 1 above to another SSD in USB enclosure.
I then booted the iMac 10,1 from the USB enclosure and it went straight in Catalina without any problems.

So, my conclusion is:
Since your mom's iMac 8,1 does not support High Sierra natively, you can only go with option 2 (APFS ROM)
Just create the USB installer (patched) and install Catalina.
On the installing windows, there is an option (Disk Utility) to partion the SSD to APFS, try it first before installing. Or better yet, do as I did in example 1 above.

 

[markapplelover]

I just share my own experience:
Example 1
iMac 24" early 2009 (iMac 9,1)
Original OS: OSX El Capitan
I removed the SSD, put it in an USB enclosure and partitioned it to APFS on another iMac 11,2 (mid 2010)
I then used the dosdude1 USB installer to install Catalina to the SSD, on the iMac 9,1.

Example 2
iMac 27" late 2009 (iMac 10,1)
Original OS: OSX Maverick
ROM version look updated, but I install High Sierra on the internal HDD anyway.
After that, I cloned the Catalina SSD in example 1 above to another SSD in USB enclosure.
I then booted the iMac 10,1 from the USB enclosure and it went straight in Catalina without any problems.

So, my conclusion is:
Since your mom's iMac 8,1 does not support High Sierra natively, you can only go with option 2 (APFS ROM)
Just create the USB installer (patched) and install Catalina.
On the installing windows, there is an option (Disk Utility) to partion the SSD to APFS, try it first before installing. Or better yet, do as I did in example 1 above.

Example 1, does it boot even without the ROM firmware flashed or upgraded when put back in? Couldn't I use target mode to do the same thing?

How do i do OPTION 2? is it my option 2 or yours?

 

[Nguyen Duc Hieu]

Example 1, does it boot even without the ROM firmware flashed or upgraded when put back in? Couldn't I use target mode to do the same thing?

How do i do OPTION 2? is it my option 2 or yours?

I installed the SSD back to iMac 9,1 (blank SSD formatted in APFS)
I plugged in the Catalina USB installer (created by Dosdude 1 patcher)
When I powered on the machine, it booted from the USB and start installing Catalina, as the SSD had already been formatted in APFS.
The machine rebooted several time, and it hanged once so I had to force it to power off. I guess the APFS rom patcher worked in the background during this hanging up, just a wild guess, as I'm new to Mac OS.
When powering it back on again, it booted up normally and continued the OS installing.

The machine has been used stably by my wife and kids for nearly a year by now.

 

[markapplelover]

Yes, not understanding the concept of installing the OS on another machine and it still being able to boot without flashing the firmware.