imac 27" 820-2828 OS not boot or random restart

[macfix]

Hello everybody

I have 3 different 820-2828 board with iMac 27" same issue,

- sometimes when load OS reboot
- sometimes when waiting login password enter reboot
- sometimes when working simple app like safari

What we tried

- known good Video board ( pulled from working machine) 3 different board
- known good OS ,Ram, PSU

when i replaced board with same PSU,Video board,rams iMac works normally.

So i think is it could be CPU core caps or some things like that???

Please help )

 

[2informaticos]

Disconnect internal HDD and try your USB test OSX.
If still the same, then try new BIOS, with clean ME.