by Hi Guys,
Hardware involved:
All motherboards based on Intel 865, 875, 848 and related
chipsets running with Intel CPUs.
The Intel 845 chipset does not exhibit these problems.
Unfortunately
Zoran based PCI cards (Capture cards, MPEG2 playback) as
manufactured by Optibase (Videoplex Express cards).
Operating system: Linux
Distribution : Redhat 9, all latest updates.
Issues: Video cards dropping frames about once every second
resulting in "stagering" video playback.
Some motherboards running certain recent VIA chipsets
(PT800) with Intel CPUs also exhibited problems.
The VIA KT400 for Athlon is OK.
After several months of intensive testing and attempts
to resolve what looks like latency issues, I have found
that all recent Intel Southbridge chips, as shown above,
cause the drop frames issue.
Optibase, who make the cards, have "given up" solving the problem.
My theory is that either the DMA or the PCI implementation
with these chipsets are flawed. There could also be issues
with the busmastering on the PCI bus. The video playback
card uses busmastering.
A different theory goes along the lines of the interupts
not being serviced fast enough from the video cards. Wether
this is a ardware issue or a linux kernel issue is not known.
It is also possible that the Zoran chips used on the video
playback boards, have some sort of flaw.
However using an NVIDIA 2 chipset does work as does VIA
chipsets for the Athlon CPU.
It has not been possible to determine what is different
between intel's implementation and Nvidia's or VIA's
implementation.
If anyone would like to comment on the above please feel
free. I have no other ideas and the whole process has
been quite draining....
Now I shall use only Nvidia 2 chipsets which forces me to
use Athlon which may not be such a bad thing.
Tony