RE: x86 TSC time warp puzzle

[Lee Revell]

On Fri, 2005-04-01 at 23:05 -0800, Pallipadi, Venkatesh wrote:
> It can be SMI happening in the platform. Typically BIOS uses some SMI
> polling 
> to handle some devices during early boot. Though 500 microseconds sounds
> a 
> bit too high.
> 

Nope, that sounds just about right.  Buggy BIOSes that implement ACPI
via SMM (or so I have been told) can stall the machine for over a
millisecond, this is why some laptops lose timer ticks at HZ=1000.  The
issue is well known by Linux audio users, as it causes big problems for
people who buy laptops for live audio use.

A list of known good/bad machines would be a tremendous help, but no one
knows the exact extent of the problem.  All Acer laptops seem to be
affected.

Hardware manufacturers (laptops anyway) don't seem to care about
anything below 1-2ms because Windows uses HZ=100 and the ASIO drivers on
that platform only go down to about ~1.5 ms latency.

Lee



-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/