A couple of people asked me to start a new thread on Kernal Panics & random shutdowns specific to PPC DP 2 Ghz G5's. I am by no means any kind of guru or technician. I try to be methodical and careful whenever I open my G5. I fully realise that I have voided my warranty several hundred times but my g5 is well and truly out of warranty so that is a non issue.
================================================

G5 Kernel Panics & Random Shutdown Analysis
From my own personal experience of being driven by desperation by random shutdowns and kernel panics to disassemble my G5 I have managed to form opinions on the possible and probable causes.
I strongly feel now that a combination of one or more of the elements listed below, occurring singly or simultaneously is the most likely cause of kernel panics or random shutdowns.
NOTE : Besides adding an extra internal case fan, swapping the seating order of the PSU fans and adding a perorated PCI slot backplane I have not performed any other modifications to my G5.

Suspected Contributing Factors :
(EDITED : Oct. 2007)
0.Badly seated CPU units.
1. Overheating caused by poor air circulation.
2. (related to above) Accumulated dust in and around the CPU cooling units and power supply.
3. Bad OSX & update-management.
4. Bad memory & PCI Cards.
5. Bad hard drives that do not show errors in Disk utility.
===============================================
I'll deal with each in turn except #1 and #2 which are related.
O. Badly Seated CPU Units
I made a page specifically for this problem. : http://www.hatsuon.net/macstuff/G5_TAKE ... _2Ghz.html
1. & 2. Overheating and Dust
Hardware Monitor :
Marcel Bresink regularly updates this wonderful app. Buy a license and set it up to display the most crucial temp readings on your desktop. It runs with a very low memory/CPU overhead.
If you live in a country with hot summers or you are a smoker then you have to think twice about where you place your G5. Never place it on or near the floor, all of those thousands of little holes in the G5 case work like vacuum cleaners when it's working hard.
Install an extra fan: I purchased a low db fan with an eye to moving as much air as possible. I mounted it just inside the front of the G5 case, above the memory DIMM slots. I ran a "Y" power line from the DVD drives power line. The Memory Heatsink Controller used to show 72.5°C (165°F) or higher, it now hovers around 61°C (141°F), a vast reduction. Remember that your G5 will shut down rather than fry a CPU or other vital component. Your PSU will simply overheat and blow if it overheats and your G5 will be dead but rather than pay Apple $400+ to replace a PSU you can buy them on the net (Google "G5 PSU") and install it yourself using my guide below.
Install perforated PCI slot backplanes:
Hunt around the PC parts shops. I have just done this this week and have noticed a slight reduction in temperature readings in this area of the case. having these extra 46 holes near my PCI slots complements the extra fan I installed in ramping up the amount of hot air shifted out of the case.
Blow out the obvious dust : Use canned air and blow out the obvious areas of the case. NOTE: Don't turn these compressd air cans upside down, they then blow out super cold air which could fracture dellicate soldering traces.
Don't forget to check all of the little holes on the front & rear of the case.
remove as many fans as possible and "polish" them, even rub them down with "ArmourAll"; a shiny, clean surface will accumulate dust much slower than a hastily wiped fan surface. think of airplane propellors.
Remove and de-dust your power supply & CPU cooling units: I put up a guide here http://www.hatsuon.net/macstuff/G5_TAKE_APART/Disassemble_G5_DP_2Ghz.html. It is not for the the technically incompetent but if you have installed a DVD or hard drive then it is do-able with care and almost guaranteed to yield better overall performance.
NOTE : During the dismantling of my G5 I found one of the bolts that hold down the CPUs to the motherboard lying loose in the case after an Apple tech here in Japan had replaced a blown PSU. Apple technicians are not infallible.
3. Bad OSX & update-management:
If you are truly serious about removing the possiblity of future kernel panics then you will now back up your important data and from scratch, re-install OSX up to 10.4.9 but . . . after the initial install from your Tiger disk . . download the COMBO UPDATER from Apple to bring you up to 10.4.9 DO NOT allow Software Update to do the installing of OSX updates. Other Apple apps like iTunes, iMovie etc are fine with using Software Update.
Prepare for installation:
Boot from your original install DVD, run Disk Utility, (a) Repair permissions TWICE. Validate your intended install partition.
NOTE : Ensure that the OSX partition is at least 50gig if you are a heavy user; OSX needs swap files on your hard drive when memory runs low.
Quit all apps:
When you do a major OSX upgrade, quit all open apps while the installation is in progress, go for a walk around the block.
Maintain OSX:
Copy the text shown below, open Terminal (It is in the Utilities folder in the Applications folder), drop the copied text into Terminals window; you'll be asked for a password, let it run. What are you doing? You are running the daily, weekly, monthly Cron (maintence) scripts which keep OSX tight and trim. It will take a minute of so to complete, watch Terminals window for the change. Note: If you leave your G5 running overnight on a Friday the scripts will run automatically.
Copy the text below, open Terminal, drop the text into Terminal's window.
===================================
sudo periodic daily weekly monthly
===================================
Safe Boot:
Reboot holding down the SHIFT key; bootup will be longer as a series of repair and maintenance routines are run in the background and you will be asked for your password. After bootup is finished simply re-boot as normal.
Get Main Menu:
This marvellous free app http://www.santasw.com/ is the ultimate maintenance tool for OSX. All you really need to do is occasionally delete or clean your system caches which can run away from you from time to time. corrupt caches can also force recurring operation errors.
4. Bad Memory & PCI / USB cards
Memory:
My G5 came with 4 "Hynix" brand memory DIMMS totallling 1 gig and I have proved to my satisfaction that at least two or all of the DIMMS are or became over time, incompatible with my G5.
Use JDEC standard memory. Google JDEC and you will find that any memory sold as JDEC meets an international standard for quality. I have 4 gig of JDEC memory in my G5 at present and have never had a problem with it.
Clean the contacts with a soft eraser and re-seat your memory dimms:
(a) Nicotine and kitchen oils buildup on DIMM contacts, remove this residue with a soft eraser.
(b) Any memory in doubt should be placed in the outer slots. trusted JDEC standard memory should inhabit the inner slots.
(c) If you have high standard memory but have had kernel panics, remove and re-seat your memory DIMMS one pair at a time to elimate bad DIMMS and to ensure a good slot connection.
PCI USB cards:
(a) Re-seat your PCI cards - including your graphics card.
(b) There are quite a few USB 2.0 cards made for PC's that can be used in a G5; look for both 3.3v and 5v in the power specs. www.ratoc.com has both 3 port and 4 port USB 2.0 cards that will work very well in any PCI user slot, my two have for two years.
5. Bad Hard Drives that do not show errors in Disk Utility:
I saved the best for last. My original 160gig SATA I hard drive that came with my G5 reported no errors in Disk Utility but I was getting random shutdowns after a fresh install. There is a guaranteed way to see if your drive has subtle errors . . . .
Apple Hardware Test:
This resides usually on Disk two of your original install DVD's. to get it going pop disk two into your dvd drive and reboot while holding down the OPTION key, this will bring up a pre-boot, volume selection screen - it will have a dark bluish background and will take a while to find what bootable volumes you have available. When it is done booting up, select Apple Hardware Test and run the medium test on your drives - it is not fast and could take an hour or more depending on your selection.
If you have a bad drive it will list it as either UPPER or LOWER as in the upper or lower drive bays in the case - I have forgotten which bay usually holds the boot drive . . . you can test for that by shutting down your G5 and seeing if it will boot after you disconnect one of two drives (if you have two).
Apple Hardware test found errors on my SATA I boot drive, I used Disk Warrior to repair the drive which I then put into an external USB 2.0 case to use for backups only. I replaced the offending drive with a 250gig Maxtor SATA II with 16mb of cache, it is noticably faster than the SATA I even though it is not working in true SATA II mode. In any case, I will be able to use this drive in my upcoming Mac Pro which does fully support SATA II.

Well, the above steps and the mainenance routines therein have kept my G5 clear of even the mildest hiccup for almost two years, absolutely no kernel panics nor random shutdowns.

IMPORTANT NOTE: If you are experiencing KP's and shutdowns often I would go straight to Step 5. to firstly eliminate this from your G5 rehabilitation program.
=============================================
Suggested Maintenance Regimen

Spring & Summer : Blow out your case every 6 weeks.
Winter : Blow out your case every two months.
System caches : Delete or clean every three months.
Complete OSX re-install : Once every year - if you are not lazy
Strip down & remove PSU for de-dusting : Every two years.

Have fun.

MIKX

NOTE : I do not "sleep" my G5. I have Energy Saver set to "Automatic".

Talk about irony, today, about 12 hours after I posted the first entry in this thread I started experiencing random shutdowns, about 6 in an hour. I ran DiskWarrior 4 and sure enough it found errors on my boot drive, Disk Utility did not find any. the drive is now healthy again.
I should have run Apple Hardware Test out of curiosity but work was pressing and I was short on time. I did take the time to blow out my case, brush he fans down etc. everything is back to normal again.

Looks rough and is only temporary but does indeed lower the CPU and Mem. Controller Heatsink temps. I keep my eye out for unusual fans and have in mind to get two small fans in one rectangular unit with a low enough profile to sit between the memory dimms and under the main CPU fans with the aim of blowing the hot air around the mem slots area to the rear fans much more quickly.

Right now I have iDVD encoding video, InDesign and Phtotshop CS2 running - CPU temps are 41°C & 42°C - Memory Controller Heatsink is at 58.1°C

i overlook around 50 g5 systems and have seen more than one KP/random shutdown/ no boot issues, yet have never had a heat related issue... normally its been bad ram (blinking power button on boot/ random hangs), bad OS (random hangs, eternal boot syndrome, errors on disk util), or bad 3rd party PCI cards (zero render/usb/firewire cards)

..oddly never seen an over-heat issue w/ a g5 (that i can remember)....

Late post - I don't get much time to check in so often.

I am beginning to think that another contributing factor is PSU power spikes.
I have come across a couple of articles on just how inefficient many PSUs are. If one has - like I do - two 4 port USB cards there is a risk that if the G5 is underload and there are several USB devices connected at the same time that an overload situation might occur. I am no electrician but it seems possible.

Thanks for those suggestions and the pics. I was doing most of these things though not as iften as you do. I don't know if I will take apart the MB but probably will pull the PSU.

On a different note I have never been impressed with AHT's ability to catch problems--especially memory-related problems. When I had a memory problem a while back neither AHT or Tech Tool Pro caught the bad chip. Memtest, which usually recommends that it run for a few hours, flagged problems within minutes. A repeat run of the test yielded the same results.

Mikx -

Thanks so much for all the reports on your G5; I think mine's identical and symptoms are sure similar - overheating, fans run away, faint high pitched hum just before computer freezes. Worried that it's a motherboard but I'm definitely going to try your countermeasures first. Was into the machine for cleaning when I first got it (had to have a MB replaced by Apple early on) but haven't been in much since and it's been about 3 years. Again, Arigato Gozaimashita.

Doitashimashita

I have moved on to a Mac Pro but still have my dual 2Ghz G5 (sentimental favourite) which I am presently restoring to 'as new' condition for re-sale. I have learned an awful lot about the quirks of my particular G5 and have noticed the the following actions usually either uncover problems or solve them, which might be useful.

#1. Create a new user with no admin rights at all - do a cold boot into this user, set energy saver to NEVER and let the G5 run overnight on a Friday - which forces the running of several repair maintenance routines. If the problem recurs then move on to #2. If no problem then it is more probably a badly maintained OSX or 3rd. party app in your admin account causing problems.

#2. Turn off the G5, Disconnect everything except mouse and keyboard, re-seat RAM and graphics card, blow out obvious dust. Reset PMU and do a NVRAM reset (boot holding down AppleKey +Option +"o" (not zero) + f.
From this point boot into SafeBoot (hold down the Shift key while booting (runs repair - maintenance routines - reboot as normal.

#3. Run Disk Warrior 4 on your boot drive - select "Replace" when it comes up.

#4. Reseat the CPU modules : If you have some computer experience and proceed slowly, methodically and carefully it is easy. You can learn how to do this on the page I made . . http://www.hatsuon.net/macstuff/G5_TAKE ... _2Ghz.html
You might as well take out the PSU and clean it too if you get this far.

I have consistently noticed that simply reseating the CPU modules has often cured some problems, it is as if the very act of removing them makes the G5 reset to zero so to speak.
I often see reports of "had motherboard replaced" "defective CPU" etc. but wonder if expansion/contraction in what is quite a hot machine can 'break' the connectivity between the CPU and the motherboard. Cetainly there are defective motherboards and CPUs but I suspect that some Apple techs opt for the easier replacement option to avoid hassles.

Number 3 (#3) above; defective hard drive has been to date by far the hardest to diagnose until http://www.prosofteng.com/ came out with their suite of hard drive tools the best of which is Drive Genius which will actually nail down and repair (if possible) exact errors much better than the dismal Apple Hardware test which often misses errors. Until Drive Genius the only practical alternative has been to buy a new drive - how wasteful! TechTool Pro looks good but I find Drive Genius friendlier and more comprehensive. Having said that one does need to learn a little about how hard drives function and how to manipulate that knowledge.
I started out in computers on the full range of Commodore Amigas which are quite nerdy compared to Apple which definitely does not want the user to muck around inside the case. On the Amigas one had to configure everything with hard drives and after the terror had subsided was actually fun and more than a little informative. The Amiga experience served me well in moving to Mac which naturally awoke my curiosity as the user seemed to have so little control over what goes on under the hood.
With Apple conforming more and more to industry standards it has become easier to come to grips with what is inside your case, even more so with the Mac Pros.
G5's remain an interesting challenge. Since I first dared to pull my G5 apart (and put it back together) in October last year it has performed flawlessly and just last week I replaced a noisy (genuine Apple part) PCI bay fan which brought it almost down to my Mac Pro's level of quietness. I truly love this machine (G5).

In my experience almost all G5 problems are 'fixable' by owners with a modicum of tech experience, patience and common sense. The times are changing, more and more G5 owners are breaking with the "void your warranty" thinking, especially now if their G5's are more than three years old and not on extended warranty. I get more than 6,000 hits per month on my "Disassemble G5" page which speaks for this newfound curiosity in G5 owners.

Good Luck with your G5, I am sure you will be able to track down the culprit(s) as I did. PM me if you hit a wall.

MIKX

Hey, MIKX, thanks for updating this post because I hadn't seen it before.

As I reply, I have a 1.8 DP G5 tower sitting dusty and unused for two years to my left. I'm ashamed to admit it, but there's a dent in its front grill from my fist because, from the moment I bought it, I experienced constant KPs that forced me to perform hard shutdowns, costing me untold time, data loss and frustration. One day, after spending about an hour writing an article for the magazine I publish, a KP wiped out all of my work because I stupidly hadn't saved. TOTALLY pissed, I punched the grill like an idiot, booted my laptop and ordered a new iMac from the Apple Store...

In my opinion, the DP G5 towers are the worst Macs Apple ever made, and the only model of the dozen or so I've owned that I regret buying. There is some inherent flaw in the hardware design - perhaps the vid card - that Apple never fessed up to, in my mind.

Anyway, my point isn't to whine but to thank you. I tried every solution I could find on MacOSG (the whole reason I joined this site) to fix my DP G5 but nothing worked. Your posts offer a few things I haven't tried, and enough time has passed that I'm willing to try n' resurrect my gorgeously designed G5 piece of crap one last time. We'll see...

Hi Everyone - Thanks largely to Mikx, I took my G5 apart and blew out all the dust, taking every component out I could. Overall, some dust and dirt but not an overwhelming amount, except on the fan/heatsink of the video card which was packed almost solid. This correlates very well to the symptom that when I put a bigger LCD monitor on, the freezes appeared to start or become worse. Clearing all the dirt and cleaning contacts of all the cards and memory appears to have completely eliminated the freezes. So, the only problems I have left at this point, appear to relate to an improper OSX update to 10.4 I did, where I didn't do a clean install. So, backing up all key data is the next step, followed by a clean install of 10.4 and hopefully we're back in the game again.

In retrospect, I can't complain too much about this machine; most electronics aren't very tolerant of heavy dirt/dust and the heavy cooling requirements these machines necessitated are pretty understandable. I guess my only wish at this point is that was a little bit easier to go further with the disassembly, to include the Power Supplies and ultimately the logic board. It appears special tools may be required for those steps or, at least a willingness to proceed more experimentally. I understand the PSU's are liquid cooled(?) and am a little nervous about taking the fasteners that appear to hold them to the main logic board out since there's no documentation on proper dis- reassembly procedures...

Anyway, so far so good.

Thanks again Mikx.

I emphathise with having lost data, been there too. The 1.8 Ghz model cetainly got some bad press and there was some talk about the firmware being at fault.
One test I developed was to disconnect everything except the mouse, keyboard, graphics card and one set of memory DIMMS - even then you should re-set the the graphics card & DIMMS.
Disconnect (not remove) all hard drives too.
Boot up the 1.8 G5 holding down the Option key which will bring up a purplish screen that will allow you to hit the eject key on the keyboard and then insert your OSX Tiger DVD which you can highlight with the mouse and then boot from.
The object of this exercise is to determine that any kernel panics or random shutdowns are hardware or software related.
Having booted to the OSX Install screen - just let the machine sit for a couple of hours. If your G5 shuts down or will not allow you to get to this point then we know that your problem is 'probably' hardware related.
If so then I recommend stripping the machine including taking out the PSU which shoiuld be opened and cleaned.
If you decide to strip it down, print out my guide :
http://www.hatsuon.net/macstuff/G5_TAKE_APART/Disassemble_G5_DP_2Ghz.html
If you have ever put a model airplane together with no left over parts then you are probably up to performing this.
While it is stripped down you can clean out everything including the interior of the PSU but more importantly remove and reset the CPU(s) module which seems to fix at least some problems.
After the re-assembly, re-connect your boot hard drive and create a new account with no admin priveliges, shut down and boot from the new account - wait for kernel panics or shut downs - if none then shut down and boot from your admin partition.
"AppZapper" (Google OSX + AppZapper) can completely remove any suspicious 3rd party apps like Flip4Mac or Microsoft Office suite (not joking at all).
Personally, if your 1.8 looks lile it will let you, I would format the main hard drive, do a clean install of OSX Tiger and then download (don't use Software Update) then 10.4.10 upgrade from Apple.

Seeing that your 1.8 G5 is collecting dust in a closet you have little to lose and a lot to gain by getting this machine up and running again.
Stripping a G5 down for the first time is indeed a little scary the first time but I have also discovered that G5's in general are pretty smart and forgiving machines; be gentle and methodical and you might be rewarded.

Good Luck. PM me if you need anything.

MIKX

Thanks,

G5 PSU's are not liquid cooled, PSU = Power Supply Unit. I think you meant "CPU's". No offense meant in correcting you
Anyway, PSU's have two internal fans which can easily get clogged with dust.
The G5 PSU sits under the floor panel: two screws hold this panel to the PSU top. there are four screws on the underside of the G5 case which hold the PSU in place. the PSU slides into guides within the case.

The only "special tools" required for dismantling a G5 are . . .
(1) 2mm Allen key with at least 15cm length (like a screw driver). For removing the lagshield bolts.
(2) "star" keys which look like Allen keys but have a star head. You can get them at any good computer parts store. You probably won't need to use them but get a set anyway.

If you have gotten to the point where you removed the CPUs then removing the PSU is only a few more steps.
================================
Removing the G5 Power Supply Unit.

1. Remove the CPU modules
2. Take a photo of the positions of the lagshield bolts and the two aluminium locating bolts; print it out. You will regret it if you don't.
3. Remove all lagshield bolts and the two (aluminium) locating bolts.
4. Remove the rear CPU fan units (depress the plastic lock bar) and slide the fans to one side - no need to disconnect them.
5. Remove the rear CPU grills - there are a lot of tiny screws involved here - be methodical.
6. Disconnect all the leads to the PSU.
7. Remove the two screws on the floor of the case above the PSU - note their position.
8. Gently tip the case over and remove the four screws on the underside of the case that secure the PSU to the floor.
9. The PSU slots into two guides; slide it to the front of the case about 2 cm and then you can remove it. Do this slowly and carefully, the PSU is heavy and bulky.

You can now remove the PSU case cover screws and blow any dust out with canned air.
That's it. Re-assemble with the same attention to detail.
==========================================
From reading your post I would say that you have no need to remove the motherboard but having gotten to the point where the PSU has been removed, you can use the extension pipe that comes with canned air to blow out any dust under the motherboard. Blow from the top of the underside of the MB so that all dust ends up on the bottom of the now empty case where it is easier to remove.

I agree with you that a clean install can do wonders. I NEVER upgrade OSX from Software Update. I ALWAYS download the COMBO update.

1. Install Tiger from the DVD only (generally there is no need to install extra languages nor printers).
2. Reboot
3. Download and install the OSX 10.4.10 COMBO update.
4. Reboot repair permissions and then use Software Update for all other upgrades.

Once you have your G5 up and running happily I would advise putting "Console" (Applications/Utilities/)on your Dock which will allow you to quickly see what is happening under the hood. It lists all major crash logs.

MIKX

Here is a list of G5 disassembly pages I currently have up on the net.
Additionally there is a link to the G5 disassembly page maintained by Carl Otto who really knows his stuff - his boldness inspired me to pull my G5 apart in the first place.

WARNING : If you are not comfortable nor competent with disassembling complex machines then read no further.
=================================================
How to strip down your G5 (not liquid cooled) G5 to the point of removing the PSU:
http://www.hatsuon.net/macstuff/G5_TAKE_APART/Disassemble_G5_DP_2Ghz.html

Removing the motherboard from a G5:
This link is a page maintained by Carl Otto :
http://g5.bhmm.net/

This is a page with a series of pics of the motherboard removed.
Note: The motherboard slides to the front of the case and then up.
http://www.hatsuon.net/macstuff/G5motherboardExtracted/RemoveG5Motherboard.html

Drastic cleaning procedure : Definitely not recommended by myself for the fainthearted nor those with little tech experience.
(If you do this - remove the battery from the motherboard!!)
http://www.hatsuon.net/macstuff/WashedG5Motherboard/WashedG5Motherboard.html

This is why I washed my motherboard . . . nicotine and grease on DIMM contacts and obviously in the DIMM and PCI slots too.
http://www.hatsuon.net/macstuff/Dirty%20DIMM.jpg

============================================
Tools required :
(1) 2mm Allen key with at least 15cm shank.
(2) Star keys (get a set, thye look a lot like Allen keys, probably won't need them but very useful for Apple computers.
3. A careful and methodical disposition.