Controling the PowerBook G3 (Pismo) Fan
17 January 2020
The PowerBook G3 (Pismo) has a small cooling fan on it's left side next to the PCMCIA assembly. Most users who have a stock CPU will have never heard, or seen this fan functioning.
The temperature limits for this machine appear to be set incredibly high, and some of the only users who have ever noticed this fan functioning are the ones who have upgraded CPUs. When the CPU reaches the machine's temperature limit the fan kicks in.
If you're worried about always running your Pismo at high temperatures the Open Firmware commands may be of use.
You can set the fan to run on boot by modifying the
thermal-info property.I haven't figured out how to vary speeds or set multiple temperature points, so if you can improve on this please let me know.
Storing values in the NVRAM
- Boot into Open Firmware by holding Command + Option/alt + O + F when booting your Pismo.
- Run the following to edit the contents of the NVRAM:
nvedit
- Run the command below which tells the NVRAM to open the power management device:
dev mac-io/via-pmu/power-mgt
- Enter the following to encode new thermal properties. Be careful to note spaces.
01010200 encode-int 00000000 encode-int encode+ 01010200 encode-int encode+ 00000000 encode-int encode+ " thermal-info" property
You can useencode-intto encode a single value, but addingencode+allows you to build up properties. In this case there are four values so we need to useencode-intandencode+.
- Press Control + C on your keyboard to exit the NVRAM editor.
- To ensure these values persist for consecutive boots, you need to store these values in the NVRAM.
Run the following commands:nvstore setenv use-nvramrc? true reset-allNote: Any data stored in the NVRAM only persists while the machine is connected to a power source. You can turn your machine off but when it’s unplugged, and it has a flat battery you will need to perform these tasks again. It may be easier to run an Open Firmware script on boot if this is something you wish to run long-term.
- Your machine will now reboot
You should hear the fans running several seconds into the boot process. If you wish to check the thermal-info properties, boot into Open Firmware and run the following commands:
dev mac-io/via-pmu/power-mgt
.properties
If you have any improvements to contribute please get in touch.
Sources
James Little - lists.apple.com
Comments
bamdad
30 September 2023
hi again, for some reason my pismo started to freeze randomly, especially on hot days when used in clamshell mode. i'm guessing this is connected to heat.. so my question is: is there a way to make these fan thresholds even more aggressive? thanks, bamdad
PermalinkGreystash - Admin
08 October 2023
Hi bamdad,
It does sound related to heat. I haven't looked into this much further after I wasn't able to improve the thresholds.
If you're running Mac OS X there's a range of fan utilities available, one of them might recognise the fan.
Otherwise It's worth applying new (and good quality) thermal paste to the CPU if you haven't done so already. Also make sure the case is dust free inside.
I've also noticed in a lot of the early PowerBooks there are some design considerations for the keyboard to be used for airflow/thermal regulation. It might be worth opening it on hot days until you can find another way to keep it cool. Keeping it closed may be trapping a lot of heat inside.
PermalinkRick
13 August 2023
It’s been a long time since I’ve used Open Firmware. Is the correct way to do this is to boot into Open Firmware, set the parameters for the fan, then make the script witty w text you provided, because the script itself will read the parameters, save them, and reapply them on each reboot? Or do I need to make a script with all the variables, and skip booting in Open Firmware?
PermalinkGreystash - Admin
13 August 2023
The script is a way to automate booting into Open Firmware and typing these parameters each time you boot. You can add all of this to a script without doing anything in Open Firmware (apart from telling Open Firmware to read the script) and you will get the same results.
As an example, your script may look like this:
You would then save this script with SimpleText with a name such as
bootscriptand place it at the root of your HD.Next you will need to restart, boot into Open firmware and tell it to load the script for every future boot:
nveditcommandThis makes Open Firmware load the script for every boot. If your computer loses power and all internal batteries are depleted you will need repeat the previous four steps again to set the script as the boot device.
Note:
I would normally test any changes by manually typing the commands before making a script in case I get something wrong.
Hopefully this makes sense!
Permalinkbamdad
03 April 2021
hey man, i've upgraded my pismo to firmware 4.1.8 in hopes of getting rid of the sleep of death bug (without success), but now there's no brightness control in os 9.0.4 (only in higher versions). the firmware readme says that to install it one must have 9.1 or higher, but i didn't think this would break some stuff in 9.0.4. i need the older os for compatibility. do you know of any way to.. downgrade the firmware? thanks in advance.
PermalinkGreystash - Admin
11 April 2021
Hi there! Sorry for the delayed response. Have you tried following the steps mentioned in this article? Please note that I have only done a successful downgrade on the Power Mac G4 MDD model. It may work but do this at your own risk, there's a chance the downgrade could brick it.
Also, have you replaced the PMU battery? There's a good chance this could be causing the sleep issues.
PermalinkPost a Comment