IGS5000 Problem?

I am not sure if this is a Photon (driver) problem or
a problem in the IGS5000 CyberPro hardware.

I am using a Conexant/BrookTree 878 video capture
chip to do bus master PCI transfers into the offscreen
overlay buffer of a IGS (Tvia) CyberPro 5000 series

My code works nicely at this point on an ATI, MediaGX,
etc. but crashes quite nastily on the CyberPro.

Actually, what crashes seems to be Photon if it tries to
do any blit operations while the memory transfers from
the Bt878 to the video ram on the CyberPro are going on
(which, as this is live TV, is basically all the time).

I am not sure if this is a PCI Grant/Latency issue, an issue
with how the IGS chip actually works during blit operations
(i.e. potential bug with concurrent PCI bus master operations
during blits), or simply an issue with the Photon driver not
having the chip setup properly to handle this (i.e. there may
be some semiphore system for scheduling blits around pci

Has anyone out there ever tried this particular combination?
(i.e. Photon + Brooktree + Tvia/Igs CyberPro)

Mike Burkey