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Old 05-27-03, 02:01 AM   #1
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Join Date: May 2003
Location: flat, steamy Champaign, IL
Posts: 36
Angry pregnant pauses in 2-D graphics; IRQ assignment?

Motherboard: supermicro P4DCE+,
dual 2GHz Xeon CPUs, 1GB RAM
Graphics card: tried both GF4 Ti4600 and GF4 MX400
Kernel: tried RH's 2.4.18-5smp,
RH's 2.4.18-3 smp bigmem,
cobbled-together 2.4.20+smp+acpi+xfs

kernel boot options: tried "noapic", "nosmp noapic" as well as default.

XFree86: 4.2.0 as shipped with RH7.3.

NVidia drivers: tried 2880 and 4363.

AGP access: tried Option "NvAGP" "0"
and default (which gave 4x AGP via agpgart).

I've tried many, many combinations of the
above kernel/graphics-card/driver/AGP,
but always find the following problem:

Many attempts to do things requiring 2-D
bit-blitting -- e.g. dragging an xterm
or even painting text into an xterm or
painting buttons on a GUI -- are liable to
be extremely slow, such that the entire
X server will lock up for tens of seconds at
a time. This makes it hard to type,
let alone work normally.

Curiously, 3-D opengl graphics don't
seem to suffer from this problem.

A similar system (Supermicro P4DCE+,
dual 2GHz Xeons, 2GB RAM) doesn't
have this problem.

The problem also goes away if I use
the "nv" driver instead of "nvidia",
but we really need the 3-D acceleration.

Suspicion: on the troublesome system,
the nvidia card always shares a
PCI interrupt (16) with the ethernet controller. On the well-running system,
the nvidia card has IRQ 10 to itself.

I can't seem to change the IRQ assignment
with tweaks like (since 01:00.0 is the nv card)
setpci -v -s 01:00.0 interrupt_line=12
setpci -v -s 01:00.0 interrupt_pin=2
The Ethernet is on the motherboard,
so I can't just move it to a different slot.

Anyone seen such a problem?
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