Gregory's Serverbad FET. it looks fine but it's not. unfortunately this means that the CPU was exposed to 5V on a voltage rail meant for something much less. the output filter caps have a 4V rating.
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 @tubetime https://www.eevblog.com/forum/testgear/agilentkeysight-infiniium-mso9000-series-motherboard-repairupgrade/ Do these logic analyzers also run PCI-E over a SATA cable to the acquisition board?  @tubetime did you need to swap the cpu, or did it survive the overvoltage? @tubetime seems a wonder it didn't die with that mosfet but maybe CPUs have features against mosfet latch up or the pmic detects it and shuts off thinking about the failure a bit more. here's the precise cause with a nice diagram. a high-side MOSFET failed in a short circuit, which would put 12V on the sensitive CPU core rail. however, the controller chip detected the overvoltage and turned on all the low side FETs (circled in green).  @tubetime ah so the pmic did protect the CPU, as expected, nice to see that even in this era such protections where already in placw, can't even begin to imagine the complicity of a pmic powering a modern Intel or AMD CPU.    @tubetime Have you considered upgrading the CPU? Looks like there are a few that are compatible with the socket and wouldn't increase the TDP. |
@tubetime ouch. It's probably fine, right? 😭