Bug#678066: Proposal to simplify PowerPC CD/DVD boot options
On 08/29/2012 07:58 PM, Rick Thomas wrote:
>
> On Aug 29, 2012, at 4:25 PM, Rick Thomas wrote:
>
>>
>> I just tried booting a PowerMac G4 with the Wheezy installer image
>> "built on 20120826-03:23" (details of where I downloaded it from, etc
>> available on request).
>>
>> The G4 is a 32-bit machine, but it seems to be offering me the choices
>> for a 64 bit machine.
>>
>> Before the "boot:" prompt it said (among other things)
>> install 64-bit processor (G5 or POWER3/4/5/6/7)
>> install32 32-bit processor (G4 or earlier)
>>
>> and when I entered <tab> at the "boot:" prompt I saw the list of options
>> install expert rescue
>> auto install32 expert32
>> rescue32 auto32
>>
At this point you can still type: install32
>> If I just hit <ret> at the "boot:" prompt it looks like it's trying to
>> boot the 64-bit kernel, which (of course) fails on the G4.
>>
>> The only unusual thing about this is that I'm booting from a USB stick
>> using Open Firmware, rather than from a physical CD-ROM. Should that
>> make any difference?
When you load yaboot binary directly from Open Firmware you are skipping
blessed stage one boot loader script. That is making the difference.
>
> I just tried booting that installer from a physical CD-ROM on the G4. I
> got the expected (32-bit) messages.
>
> So, I guess booting from a CD sets something in the OF environment that
> isn't being set when booting from a USB stick?
>
By default, PowerPC Macs boot from a CD/DVD drive by loading an Apple
specific blessed file located in an Apple_HFS partition. The blessed
file is a stage one boot loader. It is a file containing Open Firmware
commands that are figuring out whether they run on 32-bit or 64-bit
machine, followed by a boot command that loads yaboot binary while
passing appropriate arguments to it.
If yaboot binary gets loaded without arguments it will offer both 64-bit
and 32-bit options, but default to 64-bit.
>
> Is there a fix for this, or is it an un-common enough use-case to just
> need to be documented as a limitation.
>
The on-screen instructions are correct. Thus, the manual could just say
something like this: "When the machine boots, follow the on screen
instruction."
Milan
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