Capturing to a FireWire 800 drive

Question

Hi, first off, a little on the devices...
Computer:
Powerbook G4
Mac OS 10.4.5
1 GB RAM
80 GB HDD
Final Cut Studio 5.0.4
Camera:
Canon GL2 DV camera connected through FireWire 400 directly to the computer (not daisy chained through a FW800 device)
Hard Drive:
Lacie Big Disk Extreme connected through FireWire 800 directly to the computer
The issue:
When I set my external as the capture scratch in Final Cut Pro and try to capture, I keep getting dropped frames. In the past, I can capture to my Powerbook's internal hard drive from the same camera, and I've been able to capture to external FireWire 400 drives on my G4 Tower, so I know it's not an interface speed problem.
From what I hear, hooking up two devices through the same bus (not interface or port, but bus) will lower the bus speed to the lowest common demoninator, and that DV cameras operate at 200 Mbps, half the speed of FW400 drives. Looking at System Profiler, all Firewire elements are lumped under one "FireWire Bus", making me think that a single bus controls both the FW800 and FW400 interfaces. It's a triple interface drive, so so far I've been relegated to capturing to the drive through it's USB2 interface while the camera occupies the FW bus. I find it a mite bit hilarious that USB is the only interface on my system fast enough to capture to without dropped frames. So have a multi-part question here, any answers to any parts would be wonderful.
a) Did I get my definition of a bus right?
b) Is it true that the Powerbook only has a single bus controlling all FireWire interfaces?
c) Is that a standard thing? Or does a Powermac G5 have independent busses?
d) Is it really true that connecting a 200 Mbps DV camera to the computer will slow down even FW800 to 200Mbps?
e) Is there any way I can use Firewire 800 to capture or am I relegated to USB for the rest of my capturing life?
Thank you in advance for your help!
Powerbook G4   Mac OS X (10.4.5)  

Answer 1

"USB 2.0 has higher burst rates than Firewire, but it doesnt have what's called Isochronous Transactions. Isochronous Transactions are a reserved bandwidth data transmission mechanism. They provide a guaranteed rate of delivery with a guaranteed latency. This is necessary in a video stream environment. No one here has ever reported success with a USB drive."
and:
Now although USB 2.0 seems to be a lot faster than Firewire (480 megabits per second vs 400 megabits per second), it is only burst speed; the rate at which data can be transferred for a short period of time. Burst speed are generally higher than sustained speeds. Firewire on the other has transfer rates at sustained speed; the rate at which data can be transferred continuously. This is due to the difference in the chip design. This is also why Firewire is preferred when it comes to high speed peripherals like camcorders, digital cameras or hard disks.
Don't have the original sources from which these were extracted, but better to be safe than sorry.
Video capture: Fiirewire-yes, USB-no.
(unless you have P2 cards