Review Open Firmware entries?

[tubiandchill]

OK this is weird. I just reinstalled MacOS9Lives on my 12" PowerBook G4 1.33 and now sound actually plays through the laptop's speakers! There was no sound before (not even from the headphone jack) and everything else is the same. I didn't do anything different while reinstalling it. Since the battery was dead, I had to re-enter settings in Open Firmware to boot the install CD. Is there a way to review what I entered in Open Firmware? Maybe I fat-fingered something and it turned out to be beneficial for once?


This is what I thought I entered into Open Firmware from http://macos9lives.com/smforum/index.php/topic,4781.msg34262.html#msg34262:

nvedit

dev /cpus/PowerPC,G4@0

80010201 encode-int " cpu-version" property

dev /pci@F2000000/mac-io/i2s/i2s-a

" screamer" encode-string " compatible" property

device-end

Now press Ctrl + C to exit the nvram editor.

Next type the following:

Code: [Select]
nvstore

setenv use-nvramrc? true

reset-all

I also deleted all ATI extensions, along with with the HID Library and Multi-Processing folders and installed both drivers from darthnvader here: http://macos9lives.com/smforum/index.php/topic,4593.msg33188.html#msg33188

[Greystash]

After booting into Open Firmware enter the NVRAM Editor:

Code: [Select]

nvedit
Once you're in the editor you can press the Up/Down arrow keys to traverse the lines which are presently stored in the NVRAM. You can also edit the lines in place, remove them etc. and exit by pressing Ctrl + C. If you've made changes don't forget to store them again with

Code: [Select]

nvstore

[tubiandchill]

When I powered it on again, the entries were cleared, but it was still able to boot to OS 9 and still had sound coming through the speakers, though. So I guess I'll take it! 

I guess I'm confused about the lack of PRAM batteries on the 12" PowerBooks. I read the PRAM capacitor can only hold data for 15 seconds or so, and it was unplugged and without battery/power for several hours. Aren't the Open Firmware modifications stored in the PRAM?

[robespierre]

There is a region of the Flash firmware chip that is used to store the Open Firmware settable parameters.

[Greystash]

When I powered it on again, the entries were cleared, but it was still able to boot to OS 9 and still had sound coming through the speakers, though. So I guess I'll take it! 

I guess I'm confused about the lack of PRAM batteries on the 12" PowerBooks. I read the PRAM capacitor can only hold data for 15 seconds or so, and it was unplugged and without battery/power for several hours. Aren't the Open Firmware modifications stored in the PRAM?

The entries must be present still if it boots OS9, maybe there are a few blank lines you need to scroll past in the NVRAM editor?
All of my 15" and 17" G4 PowerBooks have PRAM batteries, I think they were located below/above the DVD drive? They are the lithium cell/coin type. I'm assuming the 12" PB would be the same. If all power is drained from the computer the NVRAM should clear, that's why I went to the trouble of writing OFW scripts so I don't have to re-type everything when the battery goes flat (I removed my PRAM batteries to be replaced eventually).

[tubiandchill]

There is a region of the Flash firmware chip that is used to store the Open Firmware settable parameters.

Then I can leave the laptop unplugged indefinitely and it should still be capable of booting into OS9 when I power it on again?

[tubiandchill]

When I powered it on again, the entries were cleared, but it was still able to boot to OS 9 and still had sound coming through the speakers, though. So I guess I'll take it! 

I guess I'm confused about the lack of PRAM batteries on the 12" PowerBooks. I read the PRAM capacitor can only hold data for 15 seconds or so, and it was unplugged and without battery/power for several hours. Aren't the Open Firmware modifications stored in the PRAM?

The entries must be present still if it boots OS9, maybe there are a few blank lines you need to scroll past in the NVRAM editor?
All of my 15" and 17" G4 PowerBooks have PRAM batteries, I think they were located below/above the DVD drive? They are the lithium cell/coin type. I'm assuming the 12" PB would be the same. If all power is drained from the computer the NVRAM should clear, that's why I went to the trouble of writing OFW scripts so I don't have to re-type everything when the battery goes flat (I removed my PRAM batteries to be replaced eventually).

According to https://lowendmac.com/2018/pram-and-battery-issues-in-ibooks-and-12-powerbooks/, Apple designed the 12" PowerBooks without a PRAM battery. I read your Open Firmware & OFW Script guides, but I was unable to implement a script on my end. 

[Greystash]

That's interesting! Thanks for sharing that article. For every Mac where I have modified the NVRAM contents they are wiped when all power is drained (PRAM battery + battery + mains), so unless the 12" PowerBooks are different maybe there was still some residual power left and enough to keep the changes? It would be really nice if they were preserved with total power loss.
 
If you want help getting an OFW script running feel free to send me a message, I am happy to help

[tubiandchill]

I've been tinkering with it a bit more. Found out NVRAM settings can be modified in OS X Terminal app (nvram command). Of course holding down OPT+CMD+P+R at boot still resets it, but I wonder if I write-protect usr/sbin/nvram after modifying it -- and obviously testing it a billion times before doing so -- what would happen? Do you think it would brick?
This modification is not a must, but just something I'm curious about.

[robespierre]

I've been tinkering with it a bit more. Found out NVRAM settings can be modified in OS X Terminal app (nvram command).

That is the normal way to control Open Firmware when X is installed. It is still used on Intel and ARM macs to control boot variables, where there is no OF.

Note that it only works when you sudo to the root user.

Of course holding down OPT+CMD+P+R at boot still resets it,

So what did you expect? You asked it to clear nvram. That is what command-option-P-R does.
1: "Doctor, it hurts when I do this!"
2: "So stop doing it."

but I wonder if I write-protect usr/sbin/nvram after modifying it -- and obviously testing it a billion times before doing so -- what would happen? Do you think it would brick?
This modification is not a must, but just something I'm curious about.

Makes no sense. The /usr/sbin/nvram is just the command line program. Boot variables are not stored inside it. They are stored in (drum roll) non-volatile memory. And that cannot be write protected, at all.

You can't "brick" a computer by changing its boot variables because there are ways to interrupt the boot process to regain control. The chief one being command-option-O-F on PowerPC.