[Savage40] interpolation issue

[Mark Spieth]

hi 
first of all thanks for the hard work.
I have dri on a proddr working fine (pci 8d04)
There is one problem that I have noticed.
When using savage Xv (dri-trunk 2005-02-08 debian) with mythtv where the vert lines are < total vert lines it seems to interpolate.
however it does it badly.
it seems to invert the interpolation lines between the 2 lines in question.
I dont have a copy of the data sheet so not sure what regs and bits can change this.
it seems to use the new parts from what I have determined which doiesnt have interpolation control.
Ive been experimenting for a while now but its too much like hunting in the dark.

example 2 lines

_____0_____

_000000000_

example interpolation seq
_____0_____
__0000000__
___00000___
____000____
_000000000_

when viewing this its very annoying. at first I thought it was an interlace problem but all my tests indicate not.
only happens in accel mode. If I turn dri off, its fine (but slow as).
Is it possible to get a copy of the data sheet from someone or can someone suggest some regs and bitmaps to 
I can try to fix this.
cheers
mark