How can I go back to a previous boot ROM version?

Thanks!

So, how do I do that? Do you think I should try PubMem's method again in 10.5 now?

The command is sudo bless -mount / -firmware

Oh.

Ok...I'm attempting to install OS X 10.4 on an old iMac G4. The iMac's optical drive doesn't seem to work well, so I'm booting off an install disc in my Macbook in target mode, connected via firewire. The install never finishes, giving me the error "Please try installing again." I've read several reccommendations about updating firmware to remedy this, though I'm not clear on whether in my particular situation the firmware on my Macbook on or on the iMac would be at fault. I can't (or don't know how to) update the firmware on the iMac at the moment, because the HD was erased so I can't boot from it.

The strange thing is the iMac only boots from the 10.4 disc, not the 10.1.2 discs that it came with (including the disc with Apple Hardware Test, which would be nice to do). According to disk utility the HD and all the install discs are fine. Before I start rambling...since I don't seem to be able to do anything about the firmware right now, I think my next step is to remove the iMac's airport card (which is an Apple product, but wasn't preinstalled with the computer).

Thanks!

Bummer. Ok.

Sorry I'm getting off topic here...is there any way to open the iMac's optical drive when I'm booted from an install disc (i.e. so I can try some of the discs in that drive that I hadn't tried previously)?

The iMac in the past has accepted some discs, not others.

When I run drutil in the terminal while booted from the install disc via firewire, it doesn't find any optical drives.

You know, I actually have a couple of ideas/questions, so I think I'll make a new post in the iMac section. Tx.

That sounds great...but how would I open the drive in order to put a disc in it?

Thanks...

FYI, and in case anyone else has the same issue, for my situation:

What kind of drive - slot or tray load? I'm assuming the latter given your question.

Yep.

Look on the right side of where the tray is for a small hole just big enough for a paperclip end.

Not on this model

1. Restart the computer and after the chime press and hold down the left mouse button until the disc ejects.

That worked! Unfortunately, the drive still did not, even after cleaning as you suggested. But a friend lent me an external optical drive, so all is well.

2. Press the Eject button on your keyboard.

3. Click on the Eject button in the menubar.

4. Press COMMAND-E.

As far as I could tell, none of these were options while booted from the install disc.

5. If none of the above work try this: Open the Terminal application in your Utilities folder. At the prompt enter or paste the following:

/usr/bin/drutil eject

Did nothing...and drutil list turned up no drives. I don't know if that's because the drive is totally shot or because I couldn't access it while booted from the install disc. I'd like to run AHT to find out more, but I'm having trouble with that, described here.

If this fails then try this:

Boot the computer into Single-user Mode. At the prompt enter the same command as used above. To restart the computer enter "reboot" at the prompt without quotes.

Couldn't boot in single-user mode, as far as I know, with a totally empty HD.

Ok, thanks again for the help. I'm making progess, described at the link above, and my current questions are related to RAM and AHT. So if you have suggestions about those I'd love to hear them!

At least you have made some progress. My inkling is the optical drive is dead.

I think you're right.

To run the AHT you would need the AHT disc that came with the computer, but it's unlikely you have it for that old iBook G4.

I do have it, in fact! But it's not working. Here's the situation, copied from a conversation with Kenichi Watanabe over in iMacs...

I haven't been able to run the Apple Hardware Test. I have the AHT CD that came with the computer (v1.2), and I also downloaded v1.2.6 here and burned that to a CD. In both cases, when I load the CD into the external optical drive which is connected via a firewire cable (exactly what I used for the install disc), restart, and press and hold C, the computer ignores the CD completely and boots from the HD. Any idea how to fix this? Or, is there another function I can use to achieve the same thing, maybe in single user mode?

Regarding the Apple Hardware Test CD, holding down the C key will attempt to boot from the internal optical drive. Since there is nothing in there, it boots from the internal hard drive. I would try starting up with the Option key held down. That should get you to the Startup Manager screen. If that CD is in the external FireWire drive, it should be listed as a startup disk choice. Select it and see if it will start up from it.

Right, that makes sense. Unfortunately, in both cases, when I select the CD to start up from, the screen blinks for a second and then returns to the screen where I am supposed to choose a startup disc. It does this as many times as I try to choose the CD, until I select the HD and start up from there.

When I put either CD in the drive, with the computer on and booted from the HD, the CD mounts, and Disk Utility says it's verified. But when I try to select it as a startup disc from system preferences, it doesn't show up. Ideas??

Update: I tried Hoja's reccommendation from this thread using Open Firmware, but in response to

boot cd:\diags

It says:

can't OPEN: cd:\diags

for both CDs.