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Not really. But some care is needed when swapping CPUs and the calibration must be done by booting a service CD (ASD ver 2.5.8 - the "OF" boot option, not "OS"). But the calibration can wait until you'll be sure that everything works after the swap. The computer fans will be significantly louder, but everything will work OK even without proper thermal profile.

Edit: Of course if your G5 is water cooled then everything suddently becomes painful. But I believe it's not.

[ Edited by koszer 04.06.2019 - 21:41 ]

In OpenFirmware you may see some information about your CPUS:

dev /cpus
dev PowerPC.G5@0
.properties

gives you information about CPU_0. The CPU should have status "running"

dev /
dev /cpus
dev PowerPC.G5@1
.properties

gives you information about CPU_1. The CPU should have status "standby" (or anything like this)

If CPU_1 is running, while CPU_0 sleeps, OF works, but OS may have problems. Then you have to change CPUs.
Notice: only MOS works with only one CPU. I'm not sure if other OS can switch down to 32bit.

> only MOS works with only one CPU. I'm not sure if other OS
> can switch down to 32bit.

What does 32-bit have to do with anything?

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Good point, even a single 5 punch is still 64 bit.

If you've never taken the G5 CPU outer cover off (the flat vertical panel that has a large G5 or 2 x G5 logos, if it's a double processor/2 CPUs, embossed/highlighted on it), then it can be a bit fiddly/awkward to remove, as there's a plastic rivet that's almost flush with the top of the steel panel above that panel I have described, but it can be teased-out with a sharp robust tool, like a chisel or such-like. The rivet is in 2 parts, a centre slim inner core part that splays the outer rivet into its locked position, so you need to slide the inner part out first, then put a screw of a suitable size in the hole of the centre part of the exposed rivet, and pull the outer part of the rivet out of the housing/plate.

I hope I have described this procedure sufficiently well for you to work out what to do, but if anyone else has anything else to add then by all means ......

Have you got a spare working CPU, as that can be as much of a trouble as anything else in acquiring?

You'll probably have to look around the internet for the ASD v2.58 CDs, unless someone can send/give you a copy of those files.

Thanks for all your Tipps!

And thanks AmigaHarry2 for the OF commands!

I tried them, but you have a little type in the cpu names, it has to be "PowerPC,G5@0" with a "," not with a ".".

dev /CPUs
ls

Showes only one CPU!

So I think that koszer was right and one cpu is dead.

And "dev PowerPC,G5@0" then ".properties"

Says "running" besides other infos.

"dev PowerPC,G5@1" says can't find!

Would swapping be a solution now? Because only one cpu is shown in the OF?

Or can I just pull out one cpu module?
Which? The top or bottom?

Will it boot with one cpu?

I will try later I have to go to the doctor with my dog now.

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It depends which version of G5 you have. Some of them (the earlier ones, AFAIR) would start with only 1 CPU (the "A", or - in other words - the top one), while others would need both of them seated even if the operating system of our choice requires only one. Given your machine boots at all I'd give it a shot.

Oh- thank you for correction - I typed it wrong.

There is a way to shut-down one cpu in OF:

setenv boot-args CPUS=1
reset-all

Maybe OS notice that and start with one CPU.

A guide to disassemble your G5 you can find here:
http://www.morphos-storage.net/Documentation/Apple/PowerMac_G5.pdf

G5-CPUs are "blocks" including cpu-bord and complete cooling, which can be changed as once - no big deal (if G5 is'nt watercooled).
What G5 do you have?

> There is a way to shut-down one cpu in OF: [...]
> Maybe OS notice that and start with one CPU.

As has been established some years back, this OF command just sets a flag that an OS may comply with (such as MacOSX) or may ignore (such as MorphOS).
As of MorphOS 3.10, the 2nd G5 CPU is disabled by default as opposed to pointlessly running all the time (and full-speed at that) as was happening with pre-3.10, but this has nothing to do with any OF setting.

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So, can a Dual Processor PowerMac G5 startup with MorphOS with just one CPU fitted inside the tower, or does it have to have 2 working CPUs for MorphOS to switch one into some sort of "standby" mode, or some other option(s) since v3.10?

I'm asking because I've had this failed CPU issue with one of my PowerMacs, so if one CPU/heatsink can be removed to save it from being run without any benefit to the OS (MorphOS), and put into a box/storage if not required for MorphOS use then that might be a bonus, saving one of the working CPUs for the situation where the other one fails in the future, and then you've got a spare CPU rather than scouring the internet, often in a vain attempt, to find a still working CPU of the right frequency.

> can a Dual Processor PowerMac G5 startup with MorphOS
> with just one CPU fitted inside the tower, or does it have to
> have 2 working CPUs for MorphOS to switch one into some
> sort of "standby" mode, or some other option(s) since v3.10?

Going by koszer's comment #10 it seems to depend on the specific dual-G5 PowerMac model. If it's a dual-G5 model that requires 2 CPUs installed to work, the OS can't override this. It's enough if just one CPU works while the other is broken (yet installed). In this case, some OS (MorphOS?) may require the working one to be installed in the primary slot, though. If it's a dual-G5 model that can work with 1 CPU installed, any OS will work in this config. Also here, some OS (MorphOS?) may require the CPU to be installed in the primary slot, though. At least that's how I understand it anyway :-)
Regarding the MorphOS 3.10+ feature of disabling the 2nd CPU, I guess this feature simply does not become effective in case of non-existent or broken 2nd CPU.

> if one CPU/heatsink can be removed to save it from being run without any
> benefit to the OS (MorphOS) [...] then that might be a bonus, saving one
> of the working CPUs for the situation where the other one fails in the future

This sounds reasonable, assuming your dual-G5 model can work with 1 CPU installed. The MorphOS 3.10+ feature of disabling the 2nd CPU might not be too far behind physically removing the CPU with regards to preserving service life, though.

Very strange I typed the "setenv boot-args CPUS=1" but without the
"reset-all", because I don't know exactly what will be reseted, and I'm a
bit of a "Schisser";)
Then I type "mac-boot" to continue booting, but the cd tray was pushed out,
I manually pushed it back, and no booting so I long pressed the reset
button until to shutdown the G5.
Then pushed it again to boot it, but this time I didn't hear the
click-clack of the cd drive and no booting.
So I switched it off again and on but pressed "c" to open the cd tray, but
this time pushed the hidden eject button of the cd drive to insert the tray
with no cd.

Then booted again with alt-key pressed to open the boot-menu and ctrl-y (on
a german keyboard) to go into the firmware.

There I checked the cpus, with "dev /cpus" and "ls", both cpus were shown!
Then I did "dev /cpus/PowerPC,G5@0" and ".properties".
State was "running".
Then I did "dev /cpus/PowerPC,G5@1" and ".properties".
State was here "stopped".

Note "boot-args" was still set to "CPUS=1".

Then I dared to do "mac-boot" and MorphOS booted again in full beautyness!

BTW: I have a PowerMac 7,3 with 2,3GHz.

Lets see how long it works....

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That command just reboots your computer.

I'm glad your computer is alive, but I have no idea how or why you've fixed it :)

It's normal that CPU1 is stopped in OF. OF uses only one CPU, but initializes both and send CPU1 to sleep. Has nothing to do with boot-args. CPU1 has to be "waked up" by custom-software (like a OS).
But If boot-args CPUS=1 it seems to be a bit different: Custom software won't see the second CPU - system appears as a "single chip" system - nothing to "wake up". If you have MacOS you should see that in CPU-Monitor. Nevertheless both CPUS are shown in OF.
I think, one CPU is now shut-down (hidden) by OF for custom-software, so that OS can only see one CPU and starts now properly....


Btw.: Better to be a "Schisser" than having a unusual system!

I was too happy too soon;(

After some minutes posting the above MorphOS freezes by just clicking around a bit in the screenbar;(

I rebooted but it stays at the grey screen, so I booted into firmware and there is again only one cpu shown.

Then I switched the g5 off and pulled out the bottom cpu module.

Then I wanted to try if it boots with only one cpu but nothing happened if I press the power button!?

Then I put the bottom cpu module back in, installed the heatsink, the fan and closed the case. And tried again, but the same result.
No power!

In think I need to find a new G5...

> If boot-args CPUS=1 it seems to be a bit different:
> Custom software won't see the second CPU

As said in comment #12, this is only true for "custom software" that knows this flag and complies with it, which isn't the case with MorphOS, which ignores this flag.

> system appears as a "single chip" system - nothing to "wake up".

It's the other way round. Setting the flag makes "custom software" that knows this flag and complies with it disable the 2nd CPU.

> If you have MacOS you should see that in CPU-Monitor.

...or in "About This Mac".

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OK and how about switching the CPU modules?

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Would this make sense if it doesn't powers on anymore?

Since my g5 won't turn on I leaved it over night without the powerplug plugged in.
Just now I put the powerplug in again and then the powerled flashes one time while doing this!
Is that normal or does it mean something?

Pressing the power button still doesn't turns on the machine;(

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Have a look here and see if this applies to you.

Edit: Used tinyurl because the url was breaking MZ.

[ Edited by KennyR 07.06.2019 - 21:42 ]

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Does the PSU give a "click", or does the light blink when you press the power button, or is everything silent and the light blinks only when you put the plug in?

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The second:

[b]everything is silent and the light blinks only when you put the plug in[b]

Well, I guess you have nothing to lose. Swap the CPUs. Just make sure they're seated properly. If there's an inadequate contact between CPU module and socket the machine won't power on.

I'd be interested to know the result of that ..... in fact I should have tried that when my 2.3 DP PwrMac had the same issue, but I just assumed you had to have both CPUs working/functional, so maybe that's why I never thought to try this option.

Ok, I just swapped the cpu modules and made sure to really to tighten the screws real hard.
And the G5 fires up again!

I'm writing this with my G5, yeah!

What I noticed it that the fans were blowing like hell when I boot into the bootmenu and while I'm in the firmware!?
This wasn't before, but when booting into MorphOS, the fans spins down.

Do I need to calibrate the fans?

I have the files "asd.2.6.3 (2005).dmg" and "ASD 2.5.8.dmg", but I can't burn them under MorphOS, right?
Does anyone have an .iso of these archives?
I found a dmgtoiso converter in Aminet, lets try it...

Lets see how long it last this time...

BTW:
The cpu modules look different from below!
Could it be that one cpu got burned?

G5_both_cpu_modules.jpg