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Is it possible to change the memory in an existing bios?

Yeah. It might be doable still. But not by me. I've exhausted all my knowledge on it. Oh well. It was worth a shot. And it actually taught me a few things I didn't know. So it was worth my time at least. Maybe some day I'll learn a bit more and revisit this with a fresh perspective.
 
passatgt said:
Nope :( I think its time to give up on this. 512mb is good enough :)
Click to expand...
Hi! I'm trying the same thing. How did you flash the Apple 512MB ROM onto the Dell 1GB card?
The original apple bios is 128K and the dell has only 64K ROM, do you edited the ROM to fit in the smaller chip?

If you need, I dumped a working ROM out a modified 1GB Dell MXM Card that works and it's recognized undewr macOS as 6770M 1 GB. The problem is that the ROM file is 128K and my BIOS chip is only 64K....
 
Hi! I replaced the ROM chip from a non-working mac card, which is 128K. But you can buy a 128K chip from aliexpress for example, you can look up the model number. However, the whole thing was a dead end...

I installed the card, i had boot screen but MacOS High Sierra won't boot, stops halfway(probably when it tries to load the drivers?). However, interestingly enough, if i disconnect the screen and use an external monitor with the thunderbolt port, everything is working fine...

If you can send me the ROM i can try and see if that helps with the issue or not.
 
Gpu dies are hard encoded. Yes you are at a dead end
 
passatgt said:
Hi! I replaced the ROM chip from a non-working mac card, which is 128K. But you can buy a 128K chip from aliexpress for example, you can look up the model number. However, the whole thing was a dead end...

I installed the card, i had boot screen but MacOS High Sierra won't boot, stops halfway(probably when it tries to load the drivers?). However, interestingly enough, if i disconnect the screen and use an external monitor with the thunderbolt port, everything is working fine...

If you can send me the ROM i can try and see if that helps with the issue or not.
Click to expand...
Have you tried with el capitan? high sierra is just a bunch of crap.
 
I'll try with this rom in the weekend with both El Capitan and High Sierra.

Thanks!
 
eidairaman1 said:
Gpu dies are hard encoded. Yes you are at a dead end
Click to expand...

Guess what, it's working properly now :) Boot screen, external display, brightness control, internal display, all there, just like the factory version. :clap:

IMG_0819 copy.jpg
 
Hey!
I’m looking at doing the same thing with a 6770m 1GB card, do you still have the BIOS ROM file you managed to get working?
 
Hello how are you? I'm an Italian guy with an imac 2011 with video card problems I bought a Dell 6770m video card from AliExpress I wanted to know how to make it work in my iMac for now I disconnected a BIOS chip from an iMac card and reprogrammed with Apple 6770m BIOS but iMac it gives me a black screen, how can i make it work? Thank you for your reply, thanks
 
lextar said:
Yes, I do have the file. You need to swap the bios chip with one bigger chip...
Click to expand...
Hi @lextar, went the same route as @passatgt in this thread buying a Dell 6770M 1GB card (the red one) to repair my broken iMac. Had no real luck with the original Apple HD6770M 512MB bios (boot screen OK but MacOS boot hangs then reboot, @passatgt's apparently been there as reported earlier).

Would it be possible you share that *working* HD6770M 1GB ROM? Would appreciate it very much, thank you :-)
 
lextar said:
Yes, I do have the file. You need to swap the bios chip with one bigger chip...
Click to expand...
Hello Lextar,
I have a same issue.
I swap the "cheap" BIOS (64K) by the Apple BIOS (128K) and the system show image. I Installed the MacOS but it crash in the middle the process.
Do you have a ROM file?

passatgt said:
Guess what, it's working properly now :) Boot screen, external display, brightness control, internal display, all there, just like the factory version. :clap:

View attachment 116098
Click to expand...
Hello,
do you have the file to share? I have the same issue.
 
as written previously: should i re-solder rom-chip on m5950 board to 128k version before flashing
 
semon80 said:
as written previously: should i re-solder rom-chip on m5950 board to 128k version before flashing
Click to expand...

FYI.
The ROM I posted works on the red M5950 cards only.
Recycle the chip from your dead card which is 128K and flash and solder to the replacement.
Job done!!
 

Hi, please help me I have bought M5950 red card, swapped the chip bios but when I turn on iMac... look my video please, thanks!

 
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