PowerMac G4 booting from memstick image

Tue Apr 20 01:56:39 UTC 2021

> On Apr 19, 2021, at 21:42 , Brandon Bergren <bdragon at FreeBSD.org> wrote:
> 
> On Mon, Apr 19, 2021, at 8:05 PM, Mehul Sanghvi wrote:
>> 
>> Thank you for the explanation.  I had seen something regarding SMP on 
>> the mailing list back in March
>> and so thought that it might be part of the 13.0 release.
> 
> SMP timebase fixes for G4s are a WIP still currently. I will MFC them to stable/13 once I have finished them though.
> 
> https://reviews.freebsd.org/D29136
> 
> (IIRC I need to do another rebase because of some recent changes. Will try to get back to it soon.)
> 
> I am looking for someone who has a "newer" (i.e. Quicksilver) SMP G4 to assist with submitting the platform function so I can analyze it, as I only have an ancient Graphite model that uses hardcoded timebase controls.
> 

I have a PowerMac G4 450 DP (Gigabit), but I don’t think that qualifies as newer than Quicksilver.

> In the meantime, on SMP G4 I recommend continuing to boot with SMP disabled until I can get all cases sorted out.
> 
>> 
>> I have made USB flash drive using the 13.0 memstick image, but am 
>> unable to boot from there consistently.
> 
> G4s (especially the powerbooks) can be *really* picky about which stick you're using. Of the stack of USB sticks that I own, exactly *1* consistently works. I started looking into the OpenFirmware ROM to see if I could figure out what is going on there, but so far I haven't had any ideas.
> 
> Assuming you have a stick that works, the boot command I generally use (with the iso version!) is:
> 
> boot usb1/disk at 1:2,\ppc\loader usb1/disk at 1:0

How do I burn the ISO to USB flash ?  Do I write it the same was as the memstick, using dd ? 

I have some pictures I took of the screen, since that is all I had the ability to do..  I’ll see if I can get them put up onto a website for people to see if interested.

> 
>> 
>> The first time, I got to the dialog box asking to choose Live CD, Shell 
>> or Install.  I had waited
>> A while to get to that stage, having gone through several minutes of:
>> 
>>   Root mount waiting for: CAM
>> 
>> and also
>> 
>>   aprobe1:ata1:0:1:0 CAM status: Command timeout 
>> 
>> 
>> type of messages scrolling by on the screen.  
> 
> This may be caused by a descynced timebase. At the loader prompt, do "boot kern.smp.disabled=1" (or set it in the loader environment) and see if that fixes it.
> 
>> 
>> Having gotten to the point of selecting Install,  the keyboard wouldn’t 
>> work.  An Apple keyboard, hooked up via KVM switch, which was working 
>> just fine upto that moment.  
> 
> I've seen this for some reason on ADB. I can usually work around it by using a USB keyboard. But it could be due to screwed up timers (due to timebase desync)
> 
>> I attached the keyboard directly and tried again and now I’ve got the
>> 
>>   mountroot> 
>> 
>> prompt as it couldn’t mount /dev/da0s3 the second time around.
> 
> My guess is that the timebase problems caused the controller interrupt threads to go comatose or something similar.
>> 
>> 
>> Making a third attempt now, so lets see what happens.  I might look at 
>> what Alfredo suggested and write the ISO to the USB stick and see if 
>> that works rather than the memstick.img
> 
> Only the iso gets tested. memstick.img is likely going away soon, it doesn't work very well and the iso works everywhere.
> 
>> 
>> 
>> Otherwise will just keep running NetBSD till 13.1 comes out.
>> 
>> 
>> cheers,
>> 
>>    mehul
>> 
>> 
>> 
>>> On Apr 19, 2021, at 20:46 , Mark Millard <marklmi at yahoo.com> wrote:
>>> 
>>> 
>>> 
>>> On 2021-Apr-19, at 16:34, Mehul Sanghvi <mehul.sanghvi at gmail.com> wrote:
>>> 
>>>> . . .
>>>> 
>>>> I’ll go ahead and create an image with 13.0 and see if that works.
>>> 
>>> 13.0-RELEASE was a major change, in that 32-bit PowrePC is finally using
>>> modern llvm/clang-based toochain instead of a gcc 4.2.1 based toolchain.
>>> Effectively, pre-13.0 is not as well unsupported at this point, if I
>>> understand right.
> 
> Right.
> 
>>> 
>>> In other words, it is unlikely that you would want to use a 12.x
>>> version at all unless you have reasons to be using the old toolchain.
>>> 
>>>> As I understand it 13.0 handles SMP on the G4 better, and since I have a G$ with 2 CPUs, that would be better anyway.
>>> 
>>> 13.0-RELEASE does not contain code changes to deal with FreeBSD's
>>> PowerPC problems in that area as far as I know. There is work
>>> going on in/for main in the area but some of it has not been
>>> checked into main yet, if I understand right. The range of 32-bit
>>> PowerMacs covered and if your hardware is (would be) I do not know.
>>> 
>>> There are other issues as well. For example:
>>> 
>>> Unfortunately, the FreeBSD 32-bit kernel that covers PowerMacs (G3/G4)
>>> slowly zeros out pages of user processes that it should not touch.
>>> This ends up causing some processes to crash and probably other, less
>>> obvious, issues. It is not a reliable environment. To my knowledge,
>>> this area is not under active development currently but the basic
>>> issue of what type of thing is missing was identified some time back.
>>> (The 64-bit kernel that covers G5s does not have this problem.)
> 
> I still haven't been able to reproduce this on G3/G4, but definitely concur that there is a page zeroing issue when attempting to use the 32 bit kernel on a G5 (which has a different MMU -- the kernel interacts with it via bridge mode compatibility. I've tried several times to figure out what the heck is going on but failed every time.)
> 
> By the way, I *FINALLY* figured out what is going on with moused freaking out. It ended up being an oversight in forking that lead to floating point registers getting out of sync.
> My current in-testing patch is http://drop.rtk0.net/fork_rework_3.patch -- will be submitting it soon once I finish my local testing.
> 
> This issue actually affects ppc64 as well and has probably been the source of some mystery crashes when forking.
> 
>>> There is more, but the above two are fairly major items out of the
>>> overall list.
>>> 
>>> These issues are not unique to 13.0+ as far as I know. Using 12.x
>>> likely would not avoid them.
> 
> IMO 13 is in better shape than 12.x. I am currently dogfooding it on a G4 PowerBook on a daily basis and will be continuing to fix issues here and there that have been cropping up.
> 
>>>>> On Apr 19, 2021, at 19:10 , Alfredo Dal'Ava Júnior <alfredo at freebsd.org> wrote:
> [snip]
> 
> -- 
>  Brandon Bergren
>  bdragon at FreeBSD.org
> _______________________________________________
> freebsd-ppc at freebsd.org mailing list
> https://lists.freebsd.org/mailman/listinfo/freebsd-ppc
> To unsubscribe, send any mail to "freebsd-ppc-unsubscribe at freebsd.org”

cheers,

    mehul