Did you experience a speed drop in file transfers from your Mac to an external FireWire 800 drive? If so, you should read this:
I’ll cite one important comment here:
The problem lies within the file IOFirewireSerialBusProtocolTransport.kext. If you replace it with the one from 10.5 your FireWire should work properly. One caveat, you MUST repair permissions BEFORE restarting or risk not having the replacement file recognized. If you repair permissions after restarting the replacement may not be recognized.
It’s been a long search, but finally I’ve found the answer in this great forum.
Are you scared of doing it? No panic, it’s easy. Grab the file from your Installer disk or – if you are using time machine – from your backup. Date around Juli 2009.
Make a safety copy of the file /System/Library/Extensions/IOFirewireSerialBusProtocolTransport.kext somewhere else in another folder, and copy the old file into the above mentioned folder. You’ll be asked to submit your admin password.
Now run a ‘Repair Permissions’. Either use Onyx or Snow Leopard Cache Cleaner if you don’t know how to perform a ‘Repair Permissions’. Onyx is free, sLCC costs a few dollars (absolutely worth the investment!). Or start Terminal and submit following command:
diskutil repairPermissions /
and hit ENTER ⏎. The system might ask you for your password.
Reboot. Don’t panic if your Mac should need a bit longer to boot, just wait. I’ve done it, many other Mac users have done it, and we are definitely happy now.
With the ‘new’ SnowLeopard driver I achieved some 35.6 MB/sec, with the ‘old’ driver I achieve 59.4 MB/sec. That’s a lot if you are working with large files or if you have a large hard disk to be backed up with time machine. It’ll cut the backup time by almost 50%.