EFI Modifications Leaves iMac Unbootable?

jerbare writes "In attempting to run Linux and Windows on the new iMac Core Duo, people experimenting with configuring the EFI Console/Boot loader have found they can no longer boot the machine at all. Dave Schroeder of appleintelfaq.com comments, 'We have already irreversibly lost a couple of iMacs trying to load various EFI modules'. Instructions for breaking the iMac's are presently located at the bottom of the comments."

Comments

Ugh...been there

[TripMaster Monkey]

Reminds me of a situation I faced back in the day when I was a tech at a small mom-and-pop computer repair establishment. We received a shipment of motherboards, and found out that the BIOS on every single one of them was corrupt. Since the boards wouldn't even post, the traditional remedy of flashing the BIOS via a bootable floppy was not available. Normally, we would have just boxed up the boards again and returned them for replacements, but we desperately needed those boards to fill orders.

Well, desperate times call for desperate measures...

I got to thinking, "you know...once you've started booting to an OS, that BIOS chip isn't even being used anymore....hmmm". With this in mind, I pulled a working BIOS from another board, swapped it out with the bad BIOS, and powered the system on, booting from the BIOS flash floppy. Once the board had booted to the flash program, I carefully pulled the good chip back out, and put in the bad chip. I then ran the flash program to overwrite the bad BIOS.

Long story short, it worked like a charm. I managed to revive every board in the bad shipment without incident using this unorthodox technique.

Anyway, it should be possible to rig up a similar arrangement here, although as I am unfamilliar with EFI, I'll leave the details up to someone else.

Re:Ugh...been there

[GmAz]

I did the same thing on my ASUS A7N8X-Deluxe motherboard. They shipped a bunch with their 3.3v batters running about 2.9v. Apparently this would corrupt your bios chip. Well, it did do that to mine and instead of ripping my machine apart and RMAing it, I took the bios chip from my brother-in-laws machine (I built his too and we pretty much had identical machiens) and did the swap trick. Here's a little trick for any of you wanting to try this. Before you boot up your good machine, take the bios chip out and put a piece of dental floss under it and put the chip back in. That way, when the machine is booted and you need to take it out to do the swap, just tug gently on the floss. I didn't wanna stick a metal screwdriver in there to pop it out when it was running. It worked great for me and spent $2 for two 3.3v batteries for the computers.

Re:Denial Of Service - Putting people at threat

[TheRaven64]

When the first flash BIOSes came out in the PC world there were a few viruses that would re-flash the BIOS with junk, turning the machine into a doorstop. These days most virus writers want to add your machine to a botnet, rather than destroy it, so it's probably less likely. More likely is hiding a copy of the virus in the EFI code so that it is automatically reinstated if removed when the system invokes an EFI call (resume from sleep would be my choice).