Booting from an external SSD I have a late 2009 i7 iMac that spends most of its time reading and swapping files from the 2TB hard drive, even though it’s only 40% full.

I want to buy an affordable (240GB/£160) Firewire external SSD, and install Yosemite on to it, then use that as my startup disc.

Will I get an appreciable jump in speed, or will I be limited by Firewire 800 speeds ?

Has any one tried this ?
As you know with SATA connection you get 3 to 6 Gb/s.

With Firewire you get &lt; 1 Gb/s data transfer.

To be specific:

Firewire 800 is 800 Mbits/s (Mb/s) not 800 Mbytes/s (MB/s) [8 bits in a byte] its a common misconception. so Firewire 800 is rated up to 80 MB/s.