I was told in a seminar that G5s, when connected to FW devices will IO only at the speed of the slowest FW device. So, If I hooked up an AJA IO (FW400), and a FW800 HD
(FW800 to a FW pci card), I would only get IO comparable to the FW400. Is that correct?
If so, will the newer Macs w/ PCIe slots still compromise FW performance in the same way?
Yes, that would be true if the chipset of the FW400 device does not know how to communicate on the new FW800 path. But either the FW400 or FW800 could have a mix of speeds from 100 to 400 without any problems. (An advantage over USB 2.0) I mention this difference because, in theory, a drive with both FW 800 and 400 ports could be using the FW 800 chipset and allow the 400 port to be used without detriment to another device running FW 800 on your mac. Confused yet?
What you CAN have is 2 FW800 devices with different data rates working at once on one port. One at 300 and another at 500 because they are both using one TYPE of FW on one port.
But it is my understanding that if you have a separate FW800 PCI card that you should not have to communicate on the same protocol because you are on 2 different busses. Regardless, G5's have really bad FW800 performance which has been confusing... http://www.barefeats.com
So in short, using the same BUS (i.e. built in ports) you are restricted to the lowest protocol capabilities of your lowest device... that is my understanding. Anyone have any REAL experiences?