[Veltliner]

I know this is basic, but I somehow forgot which key to press to get the splash screen where you can choose from which disc (main HD, external disc, install disc) you want to start up.

It is a key, that I press at start-up, isn't it?

[steve626]

You should hold down the option key when starting up the computer to get the selection of bootable drives.

[Veltliner]

Thanks!

Your name goes into the MacNN-book of quick replies.

(memorizing aid: I have an OPTION from which disc to start up at start-up).

[Simon]

There are actually quite a lot of these options on Macs.

• holding option is the one that lets you chose which boot partition to boot from
• c will boot from the first partition in the optical drive
• d will boot from the second partition in the optical drive
• x will force boot OS X
• option-cmd-shift-delete will bypass the primary boot volume and force boot from another
• n for netboot

[Veltliner]

Originally Posted by Simon 

There are actually quite a lot of these options on Macs.

• holding option is the one that lets you chose which boot partition to boot from
• c will boot from the first partition in the optical drive
• d will boot from the second partition in the optical drive
• x will force boot OS X
• option-cmd-shift-delete will bypass the primary boot volume and force boot from another
• n for netboot

What's a partition in the optical drive? You mean a disc in the Superdrive? What are the partitions there?

Netboot? Sounds like futuristic footwear

Force boot OS X looks like it's useful for those, who still have OS 9 on their computers...

Bypass the primary boot volume (the main HD) and boot from another: isn't that the same thing as option, only I have options when I press option?

[Simon]

Originally Posted by Veltliner 

What's a partition in the optical drive? You mean a disc in the Superdrive? What are the partitions there?

For example a DVD with different bootable volumes on it. Like the current Mac install disks. They usually have two bootable volumes. One is the actual installer, the other is AHT.

Bypass the primary boot volume (the main HD) and boot from another: isn't that the same thing as option, only I have options when I press option?

If you only have two volumes to pick from using the force alternate is faster than option.

[Art Vandelay]

I'm pretty sure 'd' will only boot to the AHT diagnostics. AHT is a firmware program, not another OS X partition.

[adamfishercox]

"D" boots to the Apple Hardware Test partition on the Apple Install Discs. Notice you can't do an AHT without the Install Discs in the drive.

[Simon]

Yeah, AHT is on the DVD not in firmware.

[Art Vandelay]

You're misunderstanding me. It was said earlier that 'd' boots to another partition on a disc. The suggestion was that it would boot to any bootable partition, such as multiple OS X partitions on a disc. I was saying that 'd' will only boot to the AHT program on a disc. Also, the AHT program is a firmware program. It is not a Mac OS program.

[adamfishercox]

Oh, yes, that may be the case, but it's hard to test, as most discs aren't partitioned anyway.