Server doesn't boot when 3 PCIe slots are populated

Polytropon freebsd at
Tue Jan 16 05:27:24 UTC 2018

On Mon, 15 Jan 2018 22:30:18 +0000, Grzegorz Junka wrote:
> I tried a different pair of NVMe cards (different adapters with 
> different SSD disks) and the result was exactly the same. Note, that the 
> pair that I tried was previously working in this motherboard without 
> problems for many months, so it's safe to assume that the addition of 
> the network card is causing this problem. But then again, the network 
> card with one of the NVMe drives works fine too.
> Could be that all three cause some sort of impedance mismatch but that's 
> kind of hard to believe - these are simple cards, there is almost no 
> circuits on the NVMe adapter and the network card is just a chipset with 
> 4 slots.

No idea if it still applies, but:

I don't know if this idea has come uo yet, but many _many_ years
ago, I was in a comparable situation. This was of course "traditional
PCI times" where a common system board had 4 - 6 PCI slots. In that
particular system, 2 NICs, an ATA "controller", a TV card, and a
sound card (5 PCI cards total + 1 AGP graphics card) were installed.
The problem was that the system wouldn't start booting after BIOS POST.
The solution was to re-arrange cards, followed by a PCI configuration
reset in the CMOS setup, followed by another boot attempt. In one
specific card configuration, the system worked as expected, and
FreeBSD (at that time, probably v4 or v5) would detect all the cards
without any problems and attach the appropriate drivers. Removing
one of the cards, or exchanging card positions (for "more convenient
cabling") would render the system non-booting again. Back to the one
configuration that worked - system booted. Let me emphasize that it
was required to reset the PCI configuration in the CMOS setup every
time such a card change was made, as returning to the "verified
locations" without doing so would _not_ let the system boot properly.

I'm not sure if it's still that "easy" with modern hardware, though.
But maybe you can try... :-)

Magdeburg, Germany
Happy FreeBSD user since 4.0
Andra moi ennepe, Mousa, ...

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