Gregory's Serverwell it boots but now the frame isn't detected. so there's something wrong with the PCI card, the cable, or the backplane itself.
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 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.   |
BTW, this is why the CPU didn't fry--the multiphase buck controller (the ADP3168) has crowbar protection in case of a shorted high-side MOSFET!