2009の英語のテクニカルガイドからだけどCPUがアッチッチで点灯かな？

Processor Diagnostic LEDs
The 8-core and quad-core riser boards include a diagnostic LED for each
processor that you can use in troubleshooting processor issues. The following
illustrations show the location of each LED and its associated processor.
These error LEDs are normally o . A red illuminated LED indicates the
associated processor may be missing or in overtemp state (PROCHOT).