Re: Clock inaccuracy seen on NVIDIA nForce2 systems

[Jesse Stockall <stockall@magma.ca>]

On Wed, 2004-10-13 at 16:30, Andy Currid wrote:
> A possible cause of this behavior is a clock synchronization issue that
> can arise on some nForce2 systems when interrupts are routed through the
> IOAPIC, and Spread Spectrum (SS) clocking is enabled. Under certain
> conditions, this can cause the IOAPIC to issue multiple interrupts to
> the CPU when it should have issued only one.
> 
> If you are experiencing clock inaccuracy on nForce2 hardware, take the
> following steps to determine if this issue may be the cause:
> 
> 1. Determine if the hardware you are using may be affected by this
>    problem. The problem is limited to MCP2 and MCP2-T hardware; it does
>    not affect MCP2-S or any nForce3 hardware. MCP2 and MCP2-T hardware
>    may be identified by the PCI device ID of the ISA bridge, which is
>    0x0060 for these devices.
> 
>    To read the bridge device ID, use 'lspci -n -s 0:1.0' . The output
>    should be of the form '0000:00:01.0 Class 0601: 10de:0060 (rev a3)'.
>    The device ID of the bridge in this example is "0060" following the
>    NVIDIA PCI vendor ID "10de".
> 
>    If your ISA bridge device ID is not 0x0060, then this issue is not
>    the cause of any clock inaccuracy you are experiencing.

lspci -n -s 0:1.0

output:  0000:00:01.0 Class 0601: 10de:0060 (rev a3)

> 
> 2. Otherwise, examine the output from 'cat /proc/interrupts'. If IRQ0
>    (the timer) is shown to be in PIC mode rather than IOAPIC mode, then
>    this issue is not the cause of any clock inaccuracy you are
>    experiencing.
> 

cat /proc/interrupts

output: 0:  179117760    IO-APIC-edge  timer

> 3. Otherwise, reboot your system and enter BIOS SETUP. Check if your
>    BIOS has a Front Side Bus (FSB) Spread Spectrum (SS) clocking option.
>    On many systems, this option is located in the "Advanced Chipset
>    Features" menu. If the option is present and enabled, disable it.
>    Boot Linux and observe the system clock over several hours to verify
>    if this has improved its accuracy.
> 

Both Front Side Bus and AGP spread spectrum are disabled.

The system is running 2.6.9-rc4 and has been up for 2 days. I'm showing
an offset of -32 seconds and growing.
	
Jesse

-- 
Jesse Stockall <stockall@magma.ca>