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iMac 2011 21,5" not booting after update, BootRom empty?

Roman78

Roman78

macrumors 6502
Original poster
May 7, 2018
380
131
Eifel - Germany
I got a 2011 21" iMac from a friend here. He told me after a security update from Sierra the machine restarts and it was dead. It's doing nothing anymore, only the fans starts to spin, but no chime and screen. SMC and PRAM-Reset won't help. So he send it to me knowing i do a little tinkering with computers (is that correct English?). hmmm

So my first idea seems to be right, the bootrom seems to be empty. I connected my CH341A onto it and read the 25L6406E i found on the Logicboard. Result is a 8 Meg file containing only FF's, so no information. I tried to read it with the UEFItool, but that gives me an error. So i think the BootRom is erased by the update and the new one failed to be written. So what can i do now? He does not made a backup of the bootrom. Now i need a BootRom for a 21,5" Late 2011. Can i use the Bootrom from a 27"? And how to edit the Serial number in it? Is it enough to get a BootRom with removed Serial Number and rewrite the Serial using the Apple Serial CD? I had downloaded the CD a wile ago, but in don't know if i still have them.
 
Hi there,

Sounds like indeed the bootrom is corrupted during the security update when it was updating..

dumping another rom to it, and flash your own serial number to it should be a fix I think..
I think a 27" bootrom firmware could also work on a 21,5" iMac and add correct s/n afterwarts.

anyway, I am pretty sure @duvelhedz has done this so with his 21,5" prototype bootrom to a 27" iMac.
Also I remember a guy over @ the big 2011 iMac GPU upgrade thread topic, posted clean bootroms over there which you can use by your self only have to add your own serial number to it.
They are blank bootrom patched bootroms for the bootrom mod from Nick !
I advise you to search for that post, should have I think everything you need.

the iMac should I think also work fine withouth a serial number btw, or another serial number not from that iMac origins.
putting the correct s/n is always reccomend since you can get iCloud problems and stuff..
 
Roman78 said:
Yeah i fond it: https://forums.macrumors.com/thread....1596614/page-116?post=27792152#post-27792152

I'll have a try. I hope the serial is the only thing to be modified.

Some lower in the thread i found this: https://forums.macrumors.com/thread....1596614/page-116?post=27794409#post-27794409
Click to expand...

yeah that looks exactly what you need !
I think duvelhedz, might save your ass here.. ;)

Anyway, you only need to put in your own serial number like @duvelhedz said.
The post of tsialex is nice, he only wants to warn duvelhedz that his serial number het spread in the wild.

this is not important for you, just use his bootrom dump, and add your own serial number, flash it back to the iMac and you should be good to go I presume..
 
Are you absolutely sure your bootrom was blank and it wasn't a bad reading? I would take your 'blank' reading and still try to open it with UEFI Tool (saw you did :( ). Since the 2011 iMac is a SandyBridge iMac you cannot take someone else's ROM dump and flash it to your logic board because the ME regions won't match. So even if your bad reading has it's ME region you can use that to at least get the board to boot correctly. (copy the ME Region to another ROM) Without a clean ME region the board will boot very slowly. I see you are in Germany how expensive is to just get a used logic board and install it? All 2011 21.5" logic boards are the same (as you know from our MXM thread) its simply just swapping the MXM card and CPU over.

using the CH341a 'black edition' software with the clip correctly on, your manufacture model etc should look like this
 

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Yes indeed, well mine reading result from the CH341a were only FF's all the 8 Meg down. On the other iMac i done a week ago for the GPU mod, I got some like yours. And that file was readable in the UEFItool.

What are ME regions? If it has something to do with regions on earth, i own three 27" at the moment. I could take a Firmware dump from one of those.

I could buy another Logicboard indeed, well it is not mine iMac. But flashing is cheaper than buying a other logicboard.
 
Roman78 said:
Yes indeed, well mine reading result from the CH341a were only FF's all the 8 Meg down. On the other iMac i done a week ago for the GPU mod, I got some like yours. And that file was readable in the UEFItool.

What are ME regions? If it has something to do with regions on earth, i own three 27" at the moment. I could take a Firmware dump from one of those.

I could buy another Logicboard indeed, well it is not mine iMac. But flashing is cheaper than buying a other logicboard.
Click to expand...

i would say buying another logic board in your case is not necceceray !
flashing back a dump from another imac and setting your s/n to it, should be enough I would say..
But im not an expert in this area..
 
So, i had some time to experimentate a little. First i indeed noticed the clip was not connected correctly. After some try and error i could read the broken Firmware from the bootrom. The UEFITool gives also an error on that bootrom-file. I also noticed, when the Clip is connected correctly, there is a green light on the logicboard. But i was able toe extract the ME-regions

So i tried the Bootrom i downloaded from the GPU topic, and i tried the one from one of mine 27". But none of those is working. I suppose it is a wrong bootrom, because they are all from the 27" and not the 21,5".

So can someone send me a BootRom from a 21,5". Ofcourse i will change the serial.
 
Roman78 said:
So, i had some time to experimentate a little. First i indeed noticed the clip was not connected correctly. After some try and error i could read the broken Firmware from the bootrom. The UEFITool gives also an error on that bootrom-file. I also noticed, when the Clip is connected correctly, there is a green light on the logicboard. But i was able toe extract the ME-regions

So i tried the Bootrom i downloaded from the GPU topic, and i tried the one from one of mine 27". But none of those is working. I suppose it is a wrong bootrom, because they are all from the 27" and not the 21,5".

So can someone send me a BootRom from a 21,5". Ofcourse i will change the serial.
Click to expand...


Here ya go.

Search for YOURMLBSERIALHERE and replace it with the serial number from your logic board. NOT your 12 digit serial that you can see. It will be printed on a label on the back of the logic board by the RAM slots. Alternaively, you could possibly copy it over from your broken dump. It is 17 digits long.
You do not need to edit the dump in any other way. It is a virginised dump with a clean ME region and is ready to be serialised with BBS.

If you are running High Sierra or newer on your machine, You WILL need to do an in place upgrade so as to update the bootrom to provide APFS support (Your internal HDD will not show up on the boot picker unless the bootrom has the code it in to recognise it)
 

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for Blanc Board serializer v2.3, see my link below, you can also us it :)
or do it manually..

I have tested this version on a 27" Mid 2011 imac, and it works.. ;)

Download link :
mega.nz

MEGA

MEGA provides free cloud storage with convenient and powerful always-on privacy. Claim your free 20GB now
mega.nz mega.nz
 
Thanks for the files.

But i think the chip is defective. First of all it got recognized as 25L6405D but it should be a 25L6406E. So i flashed the bin onto it but it did not boot. I tried to verify the content of the chip whit the file and at 6% it gives "Chip with the contents are in disagreement". So i try read the just flashed content back. The result is, the first part is there and the last part is gone, all FF's.

First i did not noticed the Software recognized the chip wrong. So maybe i killed it with that. Or it just broken by the Firmware update by the owner. I tried to flash it as 25L6405D and 25L6406E, both verify will stop at 6% whit the error.

So or my device is malfunctioning or the Chip is dead. Or what do you guys think?

25L6406E cost not much in China, but weeks waiting. Can i trust stuff from China? Can i use the 25L6406E also on all 2011 model's? I noticed the 2013 has a 25Q064A and that one does not work with the CH341a.
 
the chip detection goes also wrong for me, it usually does.
I always manually select the correct one !

I would alsostrongly reccomend you use a POMONA 5250.
These are much better than the stock one that comes with the CH341A flasher.
Try it again with the Pomona

Examples can be found here on Amazon :

Amazon.com: POMONA 5250

Amazon.com: POMONA 5250
www.amazon.com
 
As an Amazon Associate, MacRumors earns a commission from qualifying purchases made through links in this post.
The link goes to some mugs.

But do you mean the Pomona 2550 Test Clip like this one: https://www.ebay.de/itm/Pomona-5250...224455?hash=item521c6d02c7:g:s5YAAOSwHSBc2ug2

None is from Germany. The 8pins are all from China and the 16pins nearest is UK. So that would be 6-8 weeks waiting. Same as the waiting time for the Chip itself.

So you mean the chip is working only my clam is crap. Last week i did a flash for a 27" and hat worked right on. I could desolder the chip and try it right on the CH341a.

Is it possible that i damaged the Chip while i tries to flash it with the wrong settings?
 
Roman78 said:
The link goes to some mugs.

But do you mean the Pomona 2550 Test Clip like this one: https://www.ebay.de/itm/Pomona-5250...224455?hash=item521c6d02c7:g:s5YAAOSwHSBc2ug2

None is from Germany. The 8pins are all from China and the 16pins nearest is UK. So that would be 6-8 weeks waiting. Same as the waiting time for the Chip itself.

So you mean the chip is working only my clam is crap. Last week i did a flash for a 27" and hat worked right on. I could desolder the chip and try it right on the CH341a.

Is it possible that i damaged the Chip while i tries to flash it with the wrong settings?
Click to expand...

Yes that looks like the right one !
if you have used your CH341A fine in the past, it should still be ok.
but remember, these only work for a few times, getting a Panoma is always recommended for more uses that 4-5 times.

also getting a new chip is indeed a good idea, i would however first try with a Panoma and if that still does not work desolder the chip, and put on a new one..
 
Ok, ill order one of those.

I just tested the clip with a broken 2006 Logicbard of a MacBook Pro, and that worked fine. Could read, erase and rewrite the chip. After that the compare worked fine.

Are there other 8mb chips that would work in a iMac? I could try to find some on scrap hardware we have at work.
 
One more thing. I also would like a SOIC-DIP adapter. But there are 2 different, 150mil and 200mil. Which one do i need, or should i just buy both? I think this would make flashing easier for new chips and in case i have to remove some chips.

www.ebay.de

SOIC8 SOP8 to DIP8 Wide-body Seat Wide 150mil 200mil Programmer Adapter SocketWH | eBay

Finden Sie Top-Angebote für SOIC8 SOP8 to DIP8 Wide-body Seat Wide 150mil 200mil Programmer Adapter SocketWH bei eBay. Kostenlose Lieferung für viele Artikel!
www.ebay.de
 
So.. big update...

Wile waiting on the RomChips from Hongkong....

I had a broken 2013 logicboard here. So i removed the Romchip from there, flashed the firmware from above onto it and soldered into the 2011. I feel like Frankenstein....

DSC_6117_DxO.jpg

So it is working. Only thing is, although i edited the BIN-file with an hex-editor and edited the Serial into it, it does dot show up on "about my mac". So i have to fix that... but not today... i burned my fingers wile soldering... f... BGA soldering station...
 
Roman78 said:
So.. big update...

Wile waiting on the RomChips from Hongkong....

I had a broken 2013 logicboard here. So i removed the Romchip from there, flashed the firmware from above onto it and soldered into the 2011. I feel like Frankenstein....

View attachment 869705

So it is working. Only thing is, although i edited the BIN-file with an hex-editor and edited the Serial into it, it does dot show up on "about my mac". So i have to fix that... but not today... i burned my fingers wile soldering... f... BGA soldering station...
Click to expand...

great you got it working !
You can also try the blanc bowrd serializer software image i posted here above.
Let me know if it worked for you 😉
 
So i managed to add the Serial using the CD from above. Thanks again. Now i need to update the Firmware. The owner said he installed Sierra and updated it. The Firmware now is IM121.0047.B1E. This should be 2015.001. Is the latest Firmware for the 21,5" the same as for the 27"? So 82.0.0.0.0. And how to update without installing High Sierra?
 
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Roman78 said:
So i managed to add the Serial using the CD from above. Thanks again. Now i need to update the Firmware. The owner said he installed Sierra and updated it. The Firmware now is IM121.0047.B1E. This should be 2015.001. Is the latest Firmware for the 21,5" the same as for the 27"? So 82.0.0.0.0. And how to update without installing High Sierra?
Click to expand...

as far I know you can only update them firmware when upgrading to high sierra and install its security updates..

This is the official way..
 
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