Intermittent sudden loss of pisplay followed by reboot! More frequent occurrence!
Recent onset of failure to display accompanied by rapid onset of loud excessive fan speed during cold boot! Remedied by reseating CPU1 assembly! Unfortunately recurred after several successful cold reboots! Many recurrences which responded to reseating CPU1 assembly!
Finally reseating CPU1 assembly did not work! Removal of CPU1 assembly allowed the normal POST and operation of Z620! Of course with the loss of the use of full memory and 2nd CPU!
With only CPU0 Onboard Diagnostics showed RAM OK, C:\ Drive OK!
Any suggestions appreciated! Possibly remove and reapply CPU1, test CPU1 RAM, etc.