High CPU usage for hardware interrupts - NIC activation issue

I run WindowsXP(SP3) on a AsRock P4i65G mainboard, PIV-2.8G CPU, one
SATA HDD. Additionally to an onboard network controller (RTL8139) a
PCI card (RTL8169) is installed. The latter one is active. After
installation the system ran smoothly for months.
For the last two weeks, without known system changes, I have observed
a CPU usage of 50% which is attributed to hardware interrupts by
Sysinternals Process Explorer. The entire system runs slower, more or
less drastically.
BIOS version is up to date, so are drivers etc. No event protocol
messages with this respect.
I removed the AGP display adapter and used the onboard chip - no
success.
I checked the IDE mode and found UDMA5.
I tried to use the MS recommended driver checking tool "verifier.exe",
but it leads to a reproducable BSOD during boot.
I have three OS installed at this computer: W2K, WXP and Windows7
(Beta). This hardware interrupt behaviour does not occur using W2K,
Windows7(Beta) nor W-XP (Safe mode). May I assume from this that
hardware is working properly?

A workaround that I cannot explain: RTL8169 (NIC1) is connected to a
LAN, RTL8139 (NIC2) has no cable attached. When I use device manager
to disable NIC2 - no change. If I re-enable NIC2 immediately, hardware
interrupts go down to zero and remain so until next reboot.

How could I perform this automatically similar to "net start/stop
(service)"?
Any ideas for the reason of these hardware interrupts?

If you're not using RTL8139 (NIC2), disable it in BIOS instead of device
manger and see if that helps.

Using IDE mode for a SATA drive will certainly slow it down. You might want
to change that if you haven't already.

When you are in device manager, is there anything causing problems; i.e.,
yellow or red icons?

I did so; still 50 % CPU usage. Disabled the remaining NIC1 - re-
enabled it => no hardware interrupts CPU load anymore.

DevMgr shows two "Intel 82801EB UltraATA Storage Controllers", the
SATA drive is attached to the second one while CD IDE drives are
attached to the first one. The chipset does not support AHCI mode.

None.

I still cannot imagine how deactivate/re-activate acts on the
interrupts behaviour?

Download the most recent set of drivers for you motherboard.

Start by installing the chipset drivers, then uninstall (one at a time)
each of the remaining device drivers and install the newer driver for same.

And on top of that, see if there are any newer drivers for the NIC you have
installed.

thanks for replies. Problem has disappeared since I deinstalled a
deactivated port on a RS232 PCI adapter card. After reboot this port
(not physically present on card) appears in devmgmt.msc again -
despite what one should think it obviously must not be deactiavted.
Cannot figure out how NIC activation/deactivation could interact with
that.

See if this article is of any help:

Choose both the "Resources by type" and
"Resources by connection" options in the 'View' pull down list.
Look for anything that doubling up on the same IRQ number.
If you see your COM port and NIC on the using the same IRQ
that may be the cause.

Where would next door piggy backing on a Wireless Network appear?

Good question, Verizon only installed a WEP router so I don't
use Wireless as WEP is all too easy to piggy back. Now WPA2
would stop the guy next door or someone parked in a car one block over.

[QuimeraEc]

Hello

Indirectly, some programs may also generate this behavior, not just some software drivers or hardware conflicts.

It is also true that this kind of problem is difficult to reproduce (for support or test purposes) because it depends on many variables to achieve this.

There is a program that can create a situation as described by you, is called Daemon Tools (version 4 or later). This excellent piece of software installs a virtual CDROM drive and in some cases can cause a -high cpu usage- problem.