Alienware ALX X58 (2008) form factor question

I purchased an ALX X58 in 2008, this is just before they changed the chassis design to the newest one they're selling now. I cant remember what the form factor of the chassis is. One day I would like to upgrade the motherboard to keep up with the times. If anyone could help me out in figuring out what the form factor for this computer chassis is id be grateful.