Ive not seen any evidence of deckink cards specifically causing content to stutter - in use or not in use. ( What tests have people performed to arrive at this conclusion?) This is a separate issue from the stutter seen when using the video input of a decklink card.

I know that decklink cards DO frame buffer. I have timecoded video footage to prove it, taken when using SDI capture on an HD Extreme (although not composite). Buffering seems to happen more when other operations are occurring in the Mac. Also more prevalent on HD-SDI capture as it requires more bandwidth.

With regard to PCIe slots - 2007 & 2008 Macs have different PCIe architecture and will work and be configured in different ways. 2007 macs running tiger can use the PCI expansion slot utility. 2008 Macs running Leopard cannot. However, on 2008 Macs, the bandwidth/lanes is 'dynamically' allocated - depending on the card installed and slot. Bandwidth is not necessarily 'fixed'

With 2008 MacPros running Leopard, the slot next to the graphics card is the fastest PCIe2 slot. However, it shares its 'communication' with the 'north bridge' controller along with the graphics card. The Upper 2 PCIe slots share the 'South Bridge' controller with the Firewire controller and optional Airport Module. Any of these devices 'could' affect performance of the decklink card causing it to frame buffer - depending on which slot it is installed.

However, a decklink Extreme HD card is only a 4Lane PCIe1 card, so does not need to be installed in slot 2 which is a PCIe2 slot.

for more info - check out:
http://developer.apple.com/documenta...mentation.html

There are 3 different issues being reported here - so don't confuse, decklink 'frame buffering' with 'content playback stuttereing' and differences between the 'composite and SDI' inputs.

Better still - use an Active silicon LFG or Phoenix card.....

Simon