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Old 02-12-2008, 10:15 PM   #5
GrassValley_BH
Demystifier/Analogizer
 
Join Date: Apr 2007
Location: Hillsboro, OR
Posts: 5,785
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Quote:
Originally Posted by tizoast View Post
Why does every FireWire doc I read say that it's OK to chain up to 64 devices together?
Because they didn't take streaming video into account there...

Sure, you can chain a whole bunch of FireWire devices together, heck I've had 8 FireWire-IDE bridge boards daisy-chained. But it didn't work well... Eventually I ditched that setup.

Anyway, the problem is that DV transfer requires a constant 25 Mbps bandwidth. It can't be 40 Mbps now and 10 Mbps next. It needs a steady 25 Mbps transfer so every frame gets to the destination on-time. Unlike Internet streaming video, the receiving device can't buffer the data and even if it could, if the bandwidth was not steady at some point it would still run out of data.

When you daisy-chain high-bandwidth devices like hard drives in the chain, you can end up with a situation where a few devices "hog" the bus bandwidth and interrupt the steady flow of DV data. SCSI used to have a similar problem back in the day...
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