Because some people were asking about the bandwidth the Bt848 might use up
on the PCI bus I did a little benchmark.

"bonnie -s 200" with a Fireball TM 3.8 Gb using Busmaster DMA on an ASUS P6NP5

without capturing:

              -------Sequential Output-------- ---Sequential Input-- --Random--
              -Per Char- --Block--- -Rewrite-- -Per Char- --Block--- --Seeks---
Machine    MB K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU  /sec %CPU
          200  5353 76.6  5898 16.9  2363 12.1  5889 51.3  6416 10.2  37.8  0.9


while capturing full screen PAL (786x576) with 24bpp:

              -------Sequential Output-------- ---Sequential Input-- --Random--
              -Per Char- --Block--- -Rewrite-- -Per Char- --Block--- --Seeks---
Machine    MB K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU  /sec %CPU
          200  5619 69.3  5939 16.9  2334 12.0  5859 50.9  6441 10.5  37.9  0.9

The differences are small and probably within the normal error margin of
bonnie.
So, one bt848 card does not have much(any?) impact on the normal operation 
of a Linux system.
If you have several cards running this will look very differently!
The same is probably true if your Linux box is used as a file server 
with 15 (or 30) SCSI drives.
 
I tested having 2 Bt848 cards grabbing in 32 bit mode (That's almost 100MB/s!)
while running bonnie.
The xtvscreen windows showed severe pixel errors.
After a while the ide driver failed to use DMA and switched DMA off.
It continued running but the results where bad.