Duration of Blocked Interrupts

[A.L.Fransen]

Robert G. Brown wrote:
> 
> On Tue, 28 Apr 1998, Alan Cox wrote:
> 
> > 100Mbit cards have ring buffers often of about 20 frames - just servicing
> > a messier ISA interrupt will do as much delaying as the longer AIC handler
> > paths.
> 
> Right, so a design spec is "no ISA cards in a high performance
> system";-).  The PCI specs make that pretty clear.  I'm afraid I do have
> a serial/modem card and a sound card on the ISA bus, but they are low
> interrupt density and I rarely use them.  Ditto "No IDE devices", right?
> 
Interesting. A a sidenote, I might add, the later Intelchipsets (HX, TX,
FX, BX etc.) actually disable some microcode to speed up the PCI-bus if
no ISA-devices are found. I tried this with a simple generic benchmark,
and it does increase overall speed with up to 10%.

Another sidenote: At my work, we use/sell SGI-computers. The O2 (the
'toaster') has both the aic7xxx-controller and a 100Mbitcard on a
PCI-bus.
Guess what?
Problems. if (harddrive-usage >= 90% AND 100Mbit) then coredump.
Why? Because the aic7xxx has a sort of 'ISA'-way of handling interrupts
(And I quote an SGI-support engineer!), and the 100Mbit card still had
'old' 10mbit kernel-tuning. We had to increase pci-bus latency to about
128, it then functioned properly.

Greetings.

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