ampfixer
Going back a few years, but wasn't the TI chipset identified as the one to have for Sonar and Firewire? I seem to recall a thread where it was listed as a best practice.
Firewire was originally adopted as a connection favored by movie makers and used to attach movie gear.
It tended to be more adopted by the Apple users, since Apple invented it.
Apple wanted a licensing fee for each interface, so Intel came out with USB alternatives.
Firewire and now Thunderbolt always stayed a step ahead of USB, but now with USB 3.1, we probably have a break-even point again.
However, it will still be a while before we see newer USB devices.
Firewire is probably considered dead nowadays as few pieces of newer equipment support it. And Thunderbolt is very expensive, power hungry and thermally active. All the connectors are active. USB is far more universal and the newest USB 3.1 stuff with that great new connector will probably become the de-facto standard in years to come.
Back in the XP days, I had a special PCI card that had Firewire 400 and 800 ports because all my external drives were Firewire 800. (This was before e-SATA, which I use nowadays).
It did sometimes seem to be trial-and-error to find the right chipsets and drivers because some people had movie gear, others audio, and I had audio and hard drives.
These old debates always re-surface when problems come up, but I think the issue is one of just finding out what works for you. The specs haven't changed and all the parts are supposed to conform to the spec. And just when you get things working, some new update will come up and you have to re-tweak things again. That's become a major issue now with so many vendors adopting 'agile' programming techniques.
In the past, I found some versions of NVIDIA graphics updates interfered with interrupt latency and made my Firewire interface glitch. But that was quite some time ago. I still try to keep my video drivers up-to-date, even though they are mostly game updates. I do check things with latencymon after updates.
For Focusrite drivers, there is a Firewire latency setting (not really audio latency) that seems to apply to the firewire transactions and interrupts. Larger setting might make larger Firewire transactions and heavier interrupt times, while shorter latencies will use smaller chunks at more frequent intervals. At least that is my understanding.
I've found the 'Short' setting was inferior for me compared to the 'Medium' latency setting. I was able to load larger and more projects using that.
Most of my projects involve humongously complex Reaktor modules (which are single threaded), so I need all the performance per core that I can muster. My tests then are stressed that way - most bang per CPU, not most number of tracks total.