Apple's new 21.5-inch iMac borrows much from previous versions, but a dive inside the desktop computer reveals a new Thunderbolt I/O port and a GPU that's relatively easy to swap out if your mad gaming skills blow it up.

The dirty work here was done by iFixit, which specializes in tearing apart the latest gadgets to reveal what's inside and offer advice on what you should and shouldn't touch if you try the same. In this case, iFixit used mainly suction cups and a T10 Torx screwdriver to get at the iMac's guts. (Other recent iFixit investigations have targeted the iPad 2's Smart Cover as well as the iPad 2 tablet computer itself.)

As for the latest iMac, more specifically the quad-core Intel Core i5-based EMC 2428 model, iFixit found the box relatively easy to open up and dissect (it scored 7 of 10 on the iFixit repairability index). The model it explored featured a 500GB hard drive and 4GB of RAM.

One nice surprise was that you can swap out the AMD GPU without replacing the whole logic board, which hasn't always been the case on Apple products. You are warned by iFixit, however, that exposing the Intel Core i5 CPU will void your Apple warranty and that you'll need to go through the tricky work of removing the logic board from the system to get at the CPU and GPU, says Miroslav Djuric, director of technical communication for iFixit.

Other findings included that the Thunderbolt interface boasts Intel's L102IA84 EFL integrated circuit, which is similar but different from the one found in a new MacBook Pro. "Thunderbolt claims to provide 10Gbps throughput for both input and output. It appears that both PCI Express and DisplayPort receive their own 10Gbps data channel. That's nice, as you don't want your display competing with your external hard drive for bandwidth," according to iFixit.

Other innards exposed include wireless components from Atheros (WiFi) and Broadcom (Bluetooth).

Some components of the new iMac, including the LG display, are the same as in previous versions. The new iMacs cost from £999 to £1,649 in their standard configurations.