This was one of the first thin iMac and is not really serviceable so it has a 1TB SATA drive
How would it go on an external SSD, from memory this only has USB 2 or Fire Wire
so would that have the through put for an SSD ?
Got my answer:
There won't be any benefit to using the SSD on USB2—USB2 can't even keep up with a reasonably speedy spinning mechanical disk, much less a solid state one. The only reason to spring for the SSD and a USB3 case is if you intend to upgrade that machine relatively soon, and can then take advantage of the extra speed and faster interface. The situation with FW800 is marginally better, but any modern SSD is still several times faster than FW800 can support.
My iMac does have USB 3.0
This model has a 27" 2560x1440 LED-backlit 16:9 widescreen IPS display with the "cover glass fully laminated to the LCD and anti-reflective coating." The rear of the case is aluminum and is thicker in the middle and tapers to a razor thin 5 mm at the edges.
Connectivity includes four USB 3.0 ports, dual Thunderbolt ports, Gigabit Ethernet, 802.11ac Wi-Fi (802.11a/b/g/n compatible), and Bluetooth 4.0.
