Having just bought a new PC case and begun to size it up for where the mobo standoff spacers would go, I've realised that the Gigabyte GA-P55-US3L mobo isn't the standard ATX size that I thought. It appears to be some weird in-between size. Incidentally, I've not obtained the mobo yet, although I've managed to evaluate it visually by downloading its somewhat fuzzy image on the Gigabyte website.
In both the 'online' user manual and on Gigabyte's website, this mobo is described as 'form factor ATX'. I therefore assumed from the start that this was the standard ATX size 305mm X 244mm. However, when I've now looked a bit more closely at the spec., it gives the dimensions of the board as 305mm X 190mm. Well, standard ATX is, as far as I'm aware, still 305mm X 244mm, Flex ATX is 229mm X 191mm, and Micro ATX is 244mm X 210mm. So, 305mm X 190mm doesn't fit with any of the current ATX standards.
Having said that, though, the new case I've bought seems to have standoff positions that correspond to this board. Phew!
So, is this a non-standard size and should it really be described as 'ATX', implying standard ATX size?
At first, I thought this was yet another case of a manufacturer trying its hardest to use the minimum amount of materials but, given that this board doesn't have a northbridge chip, I suppose Gigabyte can be forgiven.