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HP Recommended
HP Z840 Workstation
Microsoft Windows 10 (64-bit)

Hi, when switching user, the system rebooted and then post came up with the following error:

 

929-Fatal MCA error

CBO/LLC1 error detected on CPU 0

    Core 16777216 Data L2 cache data read error - uncorrectable data

CPU: 0

Status: 0xBE20000000000051136

Misc: 0x50F0083041401086

Address: 0x00000000000000B82C0

 

Please note this PC also has the following problem:

complete freeze with no sign of life once every 2 weeks now becoming more frequent once every 3-5 days. They happen randomly sometimes browsing files using explorer, browsing firefox, or sometimes when running Photoshops.

Nothing is shown in the logs.

 

Any ideas?

This is a Z840 with dual CPU with 128Gb ram and 1080Geforce card.

5 REPLIES 5
HP Recommended

the most common cause for this error is failing memory, remove all ram from the cpu 0 sockets in order, clean the ram contacts with 99% isopropyl alcohol then spray the contacts with contact cleaner and reinsert the ram 

 

DO NOT USE TV CONTACT CLEANER, IT WILL CREATE MORE PROBLEMS

 

i recommend

 

https://caig.com/product/deoxit-gold-g5s-6/

 

or

 

https://caig.com/deoxit-d-series/

 

you can also replace the ram in cpu sockets with new modules

 

 

second cause is a failing CPU or bad contacts on cpu socket (unlikely but possible)

 

if cleaning/replacing ram does not resolve issue, try cleaning cpu/cpu contacts with deoxit spray (do not touch cpu pins!)

 

if all of the above fails, replace cpu (use same or newer cpu stepping!!)

 

Edit: also cleaning the video card contacts/pci-e socket and any other pci-e cards is strongly recommended as a poor pci-e card connection can also cause this 929 error

 

 

HP Recommended

IMG_2889.jpeg

 

Thanks, I was worried it could be a mobo or gpu issue.

Could dirty contacts  also be  the cause for the recurring system freezes I’m having?

p.s. I run it memtest86 and it didn’t spot any problem with the memory, it could be a false negative?

 

Also, in regard to the freezes, I took out half the memory and still had a freeze 2 weeks later. But I can tear everything again once I clean all the contacts. 

I think i’ll clean the cpu contacts and repaste as well. 

 

I have both the wd40 contact cleaner and isopropyl alcohol. Could I use the latter?

 

out of curiosity why not the wd40 contact cleaner? I was using it recently on the pcb components of a vintage music keyboard, should I stop?

 

 Thanks

 

 

HP Recommended

IMG_2889.jpeg

 

Thanks, I was worried it could be a mobo or gpu issue.

Could dirty contacts  also be  the cause for the recurring system freezes I’m having?

p.s. I run it memtest86 months ago and it didn’t spot any problem with the memory, but could it be a false negative?

 

Also, in regard to the freezes, I took out half the memory and still had a freeze 2 weeks later. But I can tear everything again once I clean all the contacts. 

I think i’ll clean the cpu contacts and repaste as well. 

 

I have both the wd40 contact cleaner and isopropyl alcohol. Could I use the latter?

 

out of curiosity why not the wd40 contact cleaner? I was using it recently on the pcb components of a vintage music keyboard, should I stop?

 

 Thanks

 

 

HP Recommended

sigh,............can you use products not made to the task required?

 

sure you can, although i expect the results will be similar to using a hammer to extract a tooth IE- SUBOPTIMAL!!

 

wd 40 is not really designed to clean PC contacts such as those used in a cpu socket, like tv tuner spray it will leave a residue that actually causes more issues by trapping any dust on the item you use it on

 

and isopropyl alcohol that is less than 90% will not clean dimm contacts well and will not break down any existing oxidants' that have formed on the surface

HP Recommended

Thanks!

 

I found this one in my country:

https://www.hotroxuk.com/caig-deoxit-d5-contact-cleaner-142-g-5-0-oz-d5.html 

 

which i’ll order via amazon. Is the d5 ok against the gold or any other d series?

the d5 has more solvent which takes longer to dry I think. 

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