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iMac A2115 2019 27'' 820-01236 EFI and hard disk detection

J

jadao

Member
This iMac comes from companies returns. It was EFI locked, I did the mistake to solder the bios to an adapter and read it with the medusa 3.
Instead of getting an incompatible error message because the medusa 3 doesn't support it (at least the firmware I have), the medusa read only half the chip (8MB instead of 16)...
Short story, I removed the lock but and of course it never worked because of the chip has been wiped and only half the chip size was written back.

I still have some original info (ME region and FSYS) from the half dump.
Also when I open my half dump with ME analyser it can display all the info please see attached. I have of course 2 errors an 1 warning at the end because of the size mismatch.

Found a "clean ME" on Vinafix and I have absolutely no warranty if it's clean and I used it with the original FSYS block.

iMac works well except the sata 3.5 HDD is never detected, it seems powering because I can feel the mechanic HDD, I only see the internal apple proprietary SSD.

I don't know if sata detection can be messed because of the bios I am using or it's simply the reason why iMac was returned (defect)?
Do you know any schematic close enough I can use to follow the HDD sata circuit?

Thanks!
 

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  • ME_Analyser_halfDump_Imac27_2019.txt
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J

jadao

Member
No sorry I should have mention that! HDD doesn't show in disk utility I see only the SSD, I even tried while I was there to plug in a nother hdd but same thing.

The HDD is known good because I tested it with external usb enclosure and it works fine and shows the volume.

I am suspecting a logiboard issue but the bios trick added a variable in the equation...
I can simply max out the ssd, but while I am there if I can restore the sata connexion it would be great...
 
2informaticos

2informaticos

Administrator
Staff member
You should try another BIOS, from different source.

Next time, do not touch BIOS until confirm a good backup is done.
If Medusa didn't recognize it properly, once the chip was removed from the board, you can read it with any other BIOS programmer.

When we talk about BIOS files from Internet, vinafix is the last place where I will look.
I trust more Teknisi Indonesia website.

820-01236 tk.bin

drive.google.com drive.google.com
However, I cannot assure this file is good.
Test it as is, don't mix it with your backup.
 
J

jadao

Member
I tried your Bios and it didn't start. Tried another one and had the same issue described (no Sata hdd detected).

Finally I decided to max out the original 32 GB ssd bye replacing it with another one. While doing that I just found 2 drives: the hdd and the new ssd!
I ran the fusiondrive command in terminal to combine them and all went ok.

The first time I installed the OS on the original ssd it was from a usb boot, the second time it was off the internet recovery...
Maybe some transparent updates or EFI update? Anyways it is solved.

And yes I will double check next time before I touch a bios, I always use the medusa when there is a jtag connector, and I desolder and read write with a programmer when there is no jtag... This time it was tricky I was able to read with the medusa the chip soldered on an adapter with no error. I got the error when I tried to clear the $SVS, then it was too late, my backup was half the real size... Learned my lesson:)
 
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