G5 Quad CPU Issues

[gavinstubbs09]

So I received my G5 knowing that it would have an issue, turns out it is a processor.

Ran ASD 2.6.3 and it would lock up in the middle of tests with LED #2 and #7 being illuminated, and would freeze within ten minutes. I know LED2 is a CPU failure and LED7 is a STOPCHECK light, and when it was booted under Leopard each processor core were within 10*F of CPU A and B.

My question is, is the processor toast and should I look for a replacement or should I check the LCS? With the cover off both pumps seemed to feel about the same temperature and both pumps were working. I was able to keep the thing on for a solid 45 minutes straight till I turned it off so I could take it home from work.

I'd love to repaste the processors and try that out but unfortunately my T handle screwdriver for the earlier G5s is too small for the Quad

--

Also it is a dual pump model with no leakage anywhere.

 

[MacCubed]

If you get a screwdriver, you can test the CPUs in your 2.3 G5

 

[gavinstubbs09]

If you get a screwdriver, you can test the CPUs in your 2.3 G5

My 2.3 is an Early 05

 

[MacCubed]

My 2.3 is an Early 05

Oh I thought it was a late 05... My bad

 

[gavinstubbs09]

Today's update. I repasted it last night which seemed to make it worse and it now checkstops within 30 seconds of booting. I know something isn't right here and I don't know what I need (or should) buy first.

Logic board or processors?? The LCS seems to be working fine.

Machine will boot, then CPU Overtemp LED lights up then a few seconds later the checkstop goes off. The machine is not even putting out heat when the fans are at a higher speed.

I did swap A and B processors with each other and noticed no improvements.

 

[MacCubed]

Its probably the temperature diode on the CPU card. You would need to get a new CPU card, technically you can get two dual 2.3GHz cards from a late 05 and have a 2.3GHz Quad or even a 2.0GHz Quad

 

[rawweb]

Today's update. I repasted it last night which seemed to make it worse and it now checkstops within 30 seconds of booting. I know something isn't right here and I don't know what I need (or should) buy first.

Logic board or processors?? The LCS seems to be working fine.

Machine will boot, then CPU Overtemp LED lights up then a few seconds later the checkstop goes off. The machine is not even putting out heat when the fans are at a higher speed.

I did swap A and B processors with each other and noticed no improvements.

Gavin, hope I'm not coming in too late to the party, I've got 2 spare quad processors and a working logic board I'm willing to part out, and one known working dual pump. I picked up a parts machine off CL a few months ago to get my system back online.

Before you get too far though, it really might be LCS related. A failed or clogged pump will cause the processor to heat to extreme temps and trigger the LB fail safe and ultimately shut her down. Put the computer in the coolest room possible and throw a big box fan in front of the machine at full tilt. Might get you into OS X to see what the temps are (istat or something similar) and possibly determine which pump is failing to cool. Sadly, rebuilding these dual pump assemblies is a bear and I haven't heard of anyone successfully doing it on a quad. Most success stories relate to the 04 and early 05 machines. I have a pretty lengthy thread where you can see my trials and errors and maybe learn from my mistakes.

Also, as stupid as it sounds, the processor cards and logic board connections are EXTREMELY fragile. The slightest bent pin and you're out of business. Apple makes this very clear in the tech manual and never allowed single processor card replacements, instead they opted for a complete assembly replacement. The assemblies shipped with very special instructions not to misalign the cards and allegedly came pre-aligned a certain way from the factory. Extreme caution needs to be taken every-time you tear into once of these bad boys.

Whatever the case may be, I wish you luck!

 

[MacCubed]

He said in the Slack chat that he purchased 2x 2.5GHz processor cards. As I said over there, I really hope he made sure that they come out of a Late 05 G5 and not an Early 05

 

[rawweb]

He said in the Slack chat that he purchased 2x 2.5GHz processor cards. As I said over there, I really hope he made sure that they come out of a Late 05 G5 and not an Early 05

A very easy mistake. I accidentally picked up a dual 2.5 (sold to me as a 'quad' assembly on eBay) processor assembly during my trial and errors. The seller said in their listing the processors were known working and in great condition. I wasn't even 2 seconds into tearing into the box before I realized A) I had the wrong friken parts and B) They had corrosion and signs of leaking that any naked eye could see.

Buyer beware out there!

 

[MacCubed]

A very easy mistake. I accidentally picked up a dual 2.5 (sold to me as a 'quad' assembly on eBay) processor assembly during my trial and errors. The seller said in their listing the processors were known working and in great condition. I wasn't even 2 seconds into tearing into the box before I realized A) I had the wrong friken parts and B) They had corrosion and signs of leaking that any naked eye could see.

Buyer beware out there!

I remember that, did you end up rebuilding that LCS and selling it?

 

[gavinstubbs09]

He said in the Slack chat that he purchased 2x 2.5GHz processor cards. As I said over there, I really hope he made sure that they come out of a Late 05 G5 and not an Early 05

They are late 05s, have the power terminals on the end.

Gavin, hope I'm not coming in too late to the party, I've got 2 spare quad processors and a working logic board I'm willing to part out, and one known working dual pump. I picked up a parts machine off CL a few months ago to get my system back online.

I may have to get that logic board and LCS from you, I'll see how it goes with these new processors

 

[MacCubed]

They are late 05s, have the power terminals on the end.



I may have to get that logic board and LCS from you, I'll see how it goes with these new processors

The LCS is shot, I would just buy the processor cards, it would dave money on shipping too

 

[rawweb]

I remember that, did you end up rebuilding that LCS and selling it?

Nope, it's still in the box it came in down in my basement server closet, waiting for a rainy day.

I may have to get that logic board and LCS from you, I'll see how it goes with these new processors

I'm hopeful for you, but can almost guarantee that your LCS assembly is dead in the water. You've got all the classic symptoms.

Tearing into the pumps might be your only course of action. Like I said though, in all my travels and searches I couldn't find any concrete information on anyone successfully rebuilding the late 05 dual LCS (single seems to be way easier). Not saying it can't be done, if you do, please make detailed instructions. As these systems age into their second decade, we all may need to go down this road. Ultimately, I only performed a coolant flush and determined that my A pump was just not pumping fast enough to cool the processor. I found a banged up quad on CL and got lucky and swapped the processor assembly out and it's been working like a charm ever since.

 

[gavinstubbs09]

Nope, it's still in the box it came in down in my basement server closet, waiting for a rainy day.



I'm hopeful for you, but can almost guarantee that your LCS assembly is dead in the water. You've got all the classic symptoms.

Tearing into the pumps might be your only course of action. Like I said though, in all my travels and searches I couldn't find any concrete information on anyone successfully rebuilding the late 05 dual LCS (single seems to be way easier). Not saying it can't be done, if you do, please make detailed instructions. As these systems age into their second decade, we all may need to go down this road. Ultimately, I only performed a coolant flush and determined that my A pump was just not pumping fast enough to cool the processor. I found a banged up quad on CL and got lucky and swapped the processor assembly out and it's been working like a charm ever since.

What size hose did you use? I may run down to Napa or something tomorrow and pick some up and maybe work on the LCS this weekend for the hell of it.

 

[rawweb]

What size hose did you use? I may run down to Napa or something tomorrow and pick some up and maybe work on the LCS this weekend for the hell of it.

It was pretty cheap, I took the whole assembly (processors removed) to advance auto parts and had them eyeball it. They all got a good laugh at what I was trying to do. 3/8" pretty standard tubing. I've seen folks switch to a clear tubing so they can psychically see the coolant moving through.

https://forums.macrumors.com/threads/lcs-issues-late-2005-quad.1934554/page-4 - post77

 

[gavinstubbs09]

This thing is about to go flying 300 yards off a cliff. New processors, spent 5 hours on the LCS properly flushing and rebuilding, and STILL says overtemp and stopcheck not too long after.

UGH.

 

[666sheep]

Reset SMU and try thermal calibration from ASD.

 

[rawweb]

Gavin, did you run thermal calibration? You can't change processors or their positions without running the thermal calibration.

Let us know if you need a link. There's a special version for the late 05 quads.

 

[gavinstubbs09]

Gavin, did you run thermal calibration? You can't change processors or their positions without running the thermal calibration.

Let us know if you need a link. There's a special version for the late 05 quads.

Unfortunately it checkstops as soon as the Finder icon appears after the display comes on.

Reset SMU and try thermal calibration from ASD.

I've tried the SMC reset, but unable to boot into ASD or anything.

 

[rawweb]

Not good...my guess is the LCS system has completely failed. Can you verify the pumps are getting power and running? There are portions of the pump that can get gummed up as well, the only way to clear that would be a complete tear down of the pumps. Like I said, these dual systems are a pain in the...I feel your pain.

I ultimately gambled on a quad on craigslist and swapped the entire assembly with my system.

Like I said, I've got a lot of spare parts laying around in my server closet from that other unit. My other LCS assembly at least was working (pretty sure pump A was partially clogged and or failing causing warmer temps, pump b was functioning within spec) but was able to boot and run the OS, just with a little heavier fan usage than I wanted. I wish we lived a bit closer maybe we could work something out.

 

[gavinstubbs09]

Pumps were both getting power, I used clear tubing and could see coolant moving through.

Still may have to work something out!!

Maybe I can find something that will eat the s*** out of the LCS if I let it sit overnight, what I dunno. I've heard of water and vinegar but I don't know if that would be strong enough.

 

[rawweb]

Gav, if you find something that will eat those pumps clean, let me know.

I was honestly a bit shocked myself when my flush didn't work. I sat with almost boiling water and pumped it through manually both directions multiple times for what seemed like a half hour. Nothing ever came out and the flow didn't seem to be restricted at all. It was very bizarre. I felt confident going into the recharge. I even blew air (at the lowest PSI setting with my compressor to try and dislodge anything, a bit risky but I thought why not)

I would love to see some pics of your rebuilt LCS unit with the clear tubes. Did you add taps to change and flush coolant? How did you get air gaps out during the recharge?

Side thought, I've thought about trying to figure out a way to retrofit modern pumping systems onto these things but never got much out of the brainstorming phase. Sure seems like a simple theory though.

 

[mortar]

I serviced a single pump G5 Quad LCS some years ago, and put a log online about the work that has proven quite popular. Anyway, while discussing the work with other people seeking help, some guys with the dual pump version noted that the CPU waterblocks of the dual pump version were rather impossible to clean since you can't crack them open, unlike the single pump version. The single pump rad was already quite difficult and took as much hours of boiling water and vinegar as Gavin notes above having spent on the whole rebuild. I soaked the CPU contact side of CPU blocks overnight and brushed them clean. If the dual pump has similar filters as the single pump version, no amount of flushing will unclocg those things. Also, the fact that the dual pump has sealed service ports makes it a bit harder to service, but that's still possible to overcome.

If I had to work with the dual pump version, I'd take the pumps from the LCS and get some PC coolings blocks for the CPUs, GPU ones might have the most suitable selection.

 

[gavinstubbs09]

So an update on this thing. I tore it all down once again and I was draining it in the bathroom and thought of an idea, why not try some drain cleaner? Well closest I came to that was this sink rust stain remover, which says to use rubber gloves while handling. Did I? Nope



That stuff is GNARLY. One drop fell on top of the pieces that hold each waterblock to the CPU cards and you notice it right away... It discolored it that fast. Within 5 seconds I kid you not!!



So I let that stuff sit for about 10 minutes along the bottom and sitting in the waterblock hopefully freeing up anything caked on in there. When I ran water through it came out a different color, which was also different then the solution itself:



Put some coolant in them and connected it to the G5 without any processors (since the G5 will power on and the pumps will run even if neither CPU card is attached) and the results are looking pretty good. One side has an air bubble I need to take out but the other one is dialed in! I noticed that after running the solvent there were all these little red flakes that were coming out of the LCS... whatever they are I have no idea but I think the rust stuff did the trick



So here is how it looks right now except with UV Green coolant in it, I am however deathly afraid of the hose clamps may be a source of leakage, I may run some silicone around them similar to the tubing from the factory. One pump is a bit crooked, I'll fix it probably tomorrow night as well but that is the side which is working properly!



So before I started with the stain remover stuff I connected a hose and tried to push air through the system and no matter how hard I tried I could not hear anything from the Z tube. After running the solvent through the system, it is much easier to push air through.

But if I have recommendations for anyone looking at this post in the future, use clear tubing. I used 3/8" from Ace Hardware at $1.49 a foot (bought 4ft) for the weaved stuff, it's not required and cutting it is even harder. The clear stuff is cheaper and makes it easier to see coolant flowing through.

But needless to say I think it actually looks neat with the weaved tubing and the hose clamps, gives it more of an industrial appearance (I get that idea since the back of soda machines use the same tubing I used for the LCS).

Thanks for the recommendations @rawweb and @mortar if this project continues to go south I'll look into both ideas. If it really does hit the fan I am making this a target with some tannerite and my ruger .308 hunting rifle.

 

[mortar]

Nice to see you got it sorted. The drain cleaner might not have been such a bad idea.

The reinforced PVC tubing is quite stiff. I used similar stuff as temporary tubes for draining and refilling. Spring clamps are better than the worm drives, but silicone might be a good idea if you stick with the tubing. From the looks of it, I think the original unit used epoxy sealant, actually.