Upgraded "5,1" Hangs, Restarts, Won't Chime

firstly, system:

• macpro 4,1 updated 5,1 firmware
• dual x5690 processors (delidded), dual 2.26
• 56gb of ram (7x8gb, 1 stick faulty , never bothered replace)
• gtx980 flashed mac firmware
• generic usb 3.0 card
• 4 spindle drives, ssd in second optical slot

i did processor upgrade month ago, computer has been running 24/7 since @ idle , has been stable. video card, ram, usb card, hard drives, , firmware have been installed on year w/o issue.

couple of days ago started doing heavy processing on new processors, sustained 100% processor usage across cores numerous hours. processor temperatures seemed peak under 180*f , stay there. afternoon came home find screen blank, computer restarted fine. diagnostic report stated there kernel panic intel cpu power management kext.

started run system @ full blast again, , after 30 minutes or came blank screen, time computer restart blank screen , not chime. happen have spec'ed macpro stock 2.66 processors in it, swapped gtx980's between systems , restarted fine again, cut out awhile later while doing basic file transfer no processor load.

swapped processor tray other macpro, , not start using x5690 processor tray. swapped ram across , didn't change anything, checked make sure northbridge had both it's clips (it does), , re-did thermal grease on cpu northbridge under. temperature northbridge hangs around 160*f when processors idling around 120-140*f.

couple of times have been using system when problem occurs, usb 3.0 card unmounted first, , wifi not connect network second time.

basically, system start, run short period of time, cut out again when processor tray installed. seems work better when has cooled off bit.

sure has had issue before, several hours of searching , reading didn't find hadn't tested. think have narrowed down processor tray or x5690's, have no idea , why 2 days of sustained load has caused critical failure. not sure if kernel panic has it.

think next step run each of x5690's in cpu , see if can sustain load way.

 

as update:

removed cpu b , ran computer fine 10 minutes no load, fans running @ full whole time.

after accidentally dropping processor b when reseating, noticed bent pin (that may have been caused dropping processor--unclear), bent , reseated processor b. tightened down both heat sinks as without cranking down (i using craftsman t15 screwdriver this). computer refused boot @ all.

did 3/4 loosening of heatsink screws , computer booted , ran fine @ idle 8 hours. @ time, loaded render test , let go, within few minutes computer restarted again black screen.

believe next step stress test each processor in cpu , see if 1 failing under pressure. if inconclusive, try running swapping processors across slots.

--- post merged, jan 8, 2018 ---

offhand--i replace northbridge plastic retainers , re-do thermal grease--does know correct size bolt/screw replace plastic nut?

 

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