DFS mode on the iBook 7447a.

[DarthNvader]

The iBooks that came with the 7447A/B CPU default to booing in DFS-low mode, it's not an issue for 'supported' versions Mac OS X or Linux as they have functioning Power Management, also I assume NetBSD, but I've never tried it.

However if you revert to running Mac OS 9 on the iBooks you will want to set dfs-hi in Open Firmware if you want the iBook to run at full CPU speed.

There are three words on the CPU node of OF we are concerned with, spd, set-dfs-hi, and set-dfs-low.

DFS is of course the Dramatic Frequency Switching of the 7447a/b and the 7448 if you do a swap to one of these CPU's, but the modes differ on the 7448 as it supports 1/4 frequency mode as well, tho I have not figured out exactly how to set this mode for the 7448.

So if you are interested in running an unsupported OS that does not have a functioning power manager that loads early in booting such as the classic Mac OS the process for setting dfs-hi is pretty simple.

Boot into OF and navigate to the G4 on the CPU node:

dev /cpus/@0
words
spd ( returns the current dfs-mode )
set-dfs-hi
boot

The Mac Mini G4 also has a 7447a/b, but does not have the dfs-modes in Open Firmware. So it is always dfs-hi until a supported power manager loads.

Also the 12" PowerBook G4 came with the 7447a/b so this should apply the same there as the iBook G4.

It would likely be worth figuring out the 1/4 dfs-mode for the 7448 as some users have upgraded to this CPU, even if it is not a portable unit OS X's power manager does not know how to set this mode and users may want a dramatic lower power mode available at some point. As far as I know Apple didn't release the source code for OS X's power management.kexts, so adding the proper Open Firmware functionality maybe doable.

 

[greystash]

Thanks Darth! I've just got my hands on some iBooks so I'll have to try this out

 

[DarthNvader]

Thanks Darth! I've just got my hands on some iBooks so I'll have to try this out

Good luck with it, the iBooks with the R9200 GFX run OS 9.2.2 really nice, but for a few things.

1. Some models the backlight is inverted, turning the level up from the KB sends it down, and down sends it up.

2. No AirPort Extreme Support.

3. No USB 2.0 support.

4. if you do all the right hacks the iBook will sleep, but there seem to be a crash coming out of sleep and I have no clue how to debug it????

The screen never comes back on, so unless someone know how to get MacsBugs to debug over serial and how to get a low level serial connection working on an iBook G4 it's likely never to be solved.