Hi Nikolai,

Meanwhile I've captured a similar log from another (and actually this one is
my main concern because it can not be replaced easily):

https://pastebin.com/NVfRcMww

Something is clearly different here, 8259A.pl reports all irqs are edge no
matter what. BIOS setup only offers some strange "PCI IDE IRQ mode"
(Edge/Level) and apparently it has no effect anyway.

 Such an option was common in BIOS configuration of the time, due to odd 
arrangements with early PCI ATA interfaces, such as being equipped with an 
ISA stub board with a connecting cable to route IRQ14/15 from an ISA slot.

 Anyway, this the ALi M1489/M1487 chipset and no datasheet is easily 
available (perhaps Nvidia, which bought the chipset part of ALi back in 
2006, has a copy, but I wouldn't bet on it).  A product brief is available 
that says the chipset supports PCI steering, but we can only guess how it 
works.

 Please try the debug patch I sent with the previous message and maybe 
it'll dump the PIRQ router, which may or may not help.  Choosing the 
CONFIG_PCI_GOBIOS option may also reveal something along with said patch.

  Maciej