Hi all,
often my PowerMac dual G5 with MOS 3.9 (still to update to latest MOS but this is not MOS related I think) fails to boot, the screen remains black and if I wait further minutes the fans slowly accelerate going crazy upto full speed. Every time I have to restart with the power button, often I have to try even 4 or 5 times before I finally see the grey boot screen appearing. Very frustrating. This situation has apparently worsened during the last months, while initially the issue happened very seldom. I suspect this problem may be related to the HD, which perhaps fails to speed up or to start. It is still an old SATA 1 though which always worked perfectly. Any suggestions ? Thanks.

I guess that happens after loading boot.img, right?
In most oft that cases the problem seems to be poseidon.prefs (USB-Stack). Try to delete ENVARC:Sys/poseidon.prefs and reboot without any further action.

Some hint to G5:
It is very helpfull to have a "emercency" installation on a CF-Card, fittet als slave to the internal IDE-Bus (CF2IDE-Adapter required) - the DVDRW is configured as master and you should'nt touch that config (will give troubles with Open Firmware device aliases)
If that CF has a small HFS-partition including boot.img and a big bootable SFS-partition with MOS installed (called "CF1" or anything else), then you may boot as follows from Open Firmware-prompt:

> boot cd1:,\boot.img bootdevice=CF1

Don't give CF1 a higher boot-priority than your normal boot-partition, because MOS tries to boot from the partition with highest priority (as old AOS does).

Now you are in a separate MOS-Installation and can "repair" your main-installation.....or use it as origin-testinstalltion for games or other software.

1) Check G5 with ASD.
2) Move cpu1 -> cpu2 socket and cpu2->cpu1 socket(i had similar issues and this helped)

[ Edited by zukow 11.10.2018 - 14:45 ]

Does it give any sound?
Does the white LED blink?

I'd try zukow's idea - it very much reminds me issues that I had when replacing CPU modules.

Thanks for the hints folks,
@Amigaharry2 - I have not that CF2IDE hardware, usually when I need an emergency/recovery boot I simply use the MOS installation CD though. Anyway, I don't think my system reaches the loading stage of boot.img, because when this issue happens the monitor remains in standby mode, which is still a very early stage AFAIK. Also, when this happens I think I can't hear the noise of the HD spinning, that's why I suspected it was related to the HD

@koszer: no, no sounds and no blinking

@zukow: uhm ok I still have the ASD image to burn, I will check as you suggested. I will also try to swap the CPU modules once I have some time for it.

Thnx

Update: the guy who sold me his PowerMac also had given me a link to download the ASD 2.5.8.dmg... I decided to burn it but after three attempts I gave up. The CDs seem ok but my PowerMac refuses to boot from them. Even by opening the boot menu with ALT I can't see the ASD cd as a boot option... so I can't pursue this avenue.

So it's time to swap the CPU modules then apparently :(

If the machine doesn't work even after CPU swap then I can send you some (well, maybe all of) spare CPU cards that I have. At least some of them should work. But you will need the ASD anyway, to do thermal calibration.