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Top-level
@marcan I unracked one and moved it to the bench. Plugged it in, booted fine. WTF? It took me a shockingly long time to figure out that I'd racked them and installed Ethernet and KVM cables (test lab...) but had totally failed to finish the *power* cables on Friday before leaving. But they were able to pull enough current over the *Ethernet* cable somehow to power the BMC, which controlled the front panel LEDs, so the power switch actually "worked". 4 comments
@marcan that's pretty much what I'd expected at the time, but the problem followed the Ethernet cable. I could repro with nothing else plugged in. This was (iirc) an Intel L440BX+ motherboard and an early Cisco 4006 switch. I'm pretty confident that whatever was happening, it was *way* out of spec. Intel's first couple server boards (the T440BX and L440BX+) were *weird*. Like, the T440BX powered the CPU from the PSU's 3.3V line, drawing 2x the amps most early ATX PSUs provided. @marcan ah, L440GX+, not BX+. That was the one where the AGP bus was bridged into an extra 64-bit PCI bus.  @laird That... that must really have been out of spec. If it was not PoE I have no idea how you managed to power a BMC though a transformer-coupled Ethernet link! |
Gregory's Server
@laird I bet it was the KVM cables. There's no way for Ethernet to power anything other than via PoE (which needs explicit hardware on the receiving end), but HDMI/VGA cables have a convenient 5 volt pin. It's supposed to be from the machine to the monitor, but I wouldn't at all be surprised if some random KVMs get that backwards and backfeed power into the hosts...