Other Imac 2009 - Cannot Boot From USB Following Erase

[cbjroms]

Purchased an Imac (El Capitan) a few weeks ago for a project. Having spent 25+ years using Microsoft desktops I struggled a bit with the 'Apple' way of doing things but the Imac worked beautifully.

Having finished the project, I wanted to do a factory reset to clear-off all of my data in readiness to pass the machine to another user. First problem that my non-Apple keyboard (logitech usb wireless) would not give me access to the Disk Utilities menu. So I used Terminal to get it to reboot into the right menu, went into Disk Utilities and erased the HD.

But having rebooted I cannot access (tried all the key combinations I can find on the internet) anything other than Utilities whereas I want to get into the menu that allows me to reinstall El Capitan from my Install USB. Thought I would be able to use a Terminal command but the Imac doesnt seem to recognise (not installed?) Terminal commands anymore!

In summary, my fundamental problem seems to lie with the keyboard that I am using - internet suggests others have had similar experiences with non-Apple, wireless keyboards - but am reluctant to buy another JUST to be able to boot from my USB! Is there any other way from me to restore the Terminal functiolaity?

 

[Bigwaff]

You will need wired USB keyboard, preferably Apple or 3rd party which sends Apple specific command key sequences. You may also need wired USB mouse. I keep old Apple wired keyboard and mouse around just for these circumstances when durping with older hardware.

 

[DCBassman]

For basics, any wired keyboard will work. Cmd = Windows key, otherwise, there is noting different except the Eject key.
If you've erased the disk from the recovery partition, you ought to still see that partition in the boot picker - press and hold Alt/Option until it shows. If so, boot to that and choose re-install.
Let us know what the boot picker shows.

 

[HoreaG]

If you have a built in Supedrive than you can not boot from USB. I once found what needs to be modified to circumvent this, but can not find it anymore.

 

[DCBassman]

If you have a built in Supedrive than you can not boot from USB. I once found what needs to be modified to circumvent this, but can not find it anymore.

Almost every Intel Mac I've had has a built-in optical drive. They all boot from USB, without exception.

 

[HoreaG]

But we speak here not about all the intel macs but about the 2009 a 2009 iMac. The problem is found with the 2009-2011 iMacs.

 

[DCBassman]

But we speak here not about all the intel macs but about the 2009 a 2009 iMac. The problem is found with the 2009-2011 iMacs.

Never had a problem with any iMacs from that period. Please point me to some details of this.

 

[HoreaG]

Never had a problem with any iMacs from that period. Please point me to some details of this.

Well, take an iMac from that period that was delivered with a Superdrive. Put a bootable pendrive into one of its USB ports. Start the iMac and press at the same time the Option key for choosing the drive you want to boot from. You will notice it shows all bootable drives except the ones connected trough USB.
Apple blocked booting from USB in the microcode. As told before I once found a site (in fact the blog of some guy) where it was explained which lines in the microcode you have to comment out to lift the restriction.

I personally experienced this with 27" iMacs from 2009 and 2010 but not 2011. It is said the 2011 should behave the same, but in my experience I could boot some of my 2001 iMacs from USB. (some = the ones where I wanted to install a new OS, the others I did not bother I dont know; in total I have 4 and booted two from USB)

 

[DCBassman]

Well, take an iMac from that period that was delivered with a Superdrive. Put a bootable pendrive into one of its USB ports. Start the iMac and press at the same time the Option key for choosing the drive you want to boot from. You will notice it shows all bootable drives except the ones connected trough USB.
Apple blocked booting from USB in the microcode. As told before I once found a site (in fact the blog of some guy) where it was explained which lines in the microcode you have to comment out to lift the restriction.

I personally experienced this with 27" iMacs from 2009 and 2010 but not 2011. It is said the 2011 should behave the same, but in my experience I could boot some of my 2001 iMacs from USB. (some = the ones where I wanted to install a new OS, the others I did not bother I dont know; in total I have 4 and booted two from USB)

Absolutely not my experience. My first iMac was a 2009 27", and it booted fine from everything. 2011 21.5 also fine. This is, beyond question, something completely new to me, and doesn't make sense even by Apple's skewed logic. Apple has definitive guides for making bootable USB installers, so why would it restrict some machines from using them?

 

[HoreaG]

Well, take an iMac from that period that was delivered with a Superdrive. Put a bootable pendrive into one of its USB ports. Start the iMac and press at the same time the Option key for choosing the drive you want to boot from. You will notice it shows all bootable drives except the ones connected trough USB.
Apple blocked booting from USB in the microcode. As told before I once found a site (in fact the blog of some guy) where it was explained which lines in the microcode you have to comment out to lift the restriction.

Absolutely not my experience. My first iMac was a 2009 27", and it booted fine from everything. 2011 21.5 also fine. This is, beyond question, something completely new to me, and doesn't make sense even by Apple's skewed logic. Apple has definitive guides for making bootable USB installers, so why would it restrict some machines from using them?

Dont ask me, others reported this too. Did you 2009 come factory equipped with a Superdrive?

 

[DCBassman]

Dont ask me, others reported this too. Did you 2009 come factory equipped with a Superdrive?

Unibody iMacs always had a superdrive, without exception. Never seen an earlier aluminium one without one, either. You'd have had to specifically request it to be deleted on order, and while that may well have been an option, the booting of the machine wouldn't be affected. Otherwise I would not have been able to boot mine at all, because my SuperDrive was unserviceable...and I doubt any firmware could be made to be aware of that.
Now, if we're talking PowerPC machines, different story, but those were much earlier.