Dual-Core Xeon high usage on one core

[GiganticDays]

Dual-Core Xeon 3040 in server running SBS 2003 Premium, Exchange Server and SQL Server

Recently been getting reports from this server that "The processor is experiencing a low level of idle time".

Been getting that message for a couple of weeks.

On checking in Task Manager System Idle Process is at 95 - 99% but looking at the performance, CPU history shows one core running at max and one idle. Is that normal?
Under normal use this SQL Server, Exchange etc. would be running during office hours, but the server should be idle outside of those times.

[GiganticDays]

I know this topic is getting on a bit, but I still don't have a resolution. Anyone?

[GroundZero3]

Do you have any kind of antivirus running on it? How many mailboxes are you hosting on this box?

when you are looking at the preformance are you using the preformance monitor so you can see the preformance over time? Not just what is currently going on

Windows Performance Monitor

How much ram do you have installed? (just curious)

I assume you have all the latest windows, exchange, sql updates installed correct?

[GiganticDays]

We're currently running Vipre Business Standard having just changed from Trend Micro Worry-Free Business Security (we thought that was the culprit).

I rescheduled the ntbackup and virus scans so they don't coincide but that hasn't helped. The error report shows the last occurrence at around 5.00am but neither the backup nor the virus scans are running at that time.

I've just had a quick look with perfmon and interrupts/sec are permanently at the top of the scale.
CPU time is around 40-50% but the server is currently in use so I suppose that's normal.

The server has 4Gb RAM and all updates installed.

[GiganticDays]

Still trying to resolve this.

What I can't understand is why one CPU is always running at around 80-100% while the other is virtually idle.

Edit : On more detailed investigation it transpires that the excessive cpu usage is "privileged mode". "User mode" usage is similar across both cpus.

That's a little beyond my knowledge at the moment.

Looking at Task manager - System Idle Process is ranging from high 80s% to high 90s% - nothing seems to be hogging the cpu but in the Performance section one core is flat out and the other idle.