I had a PC in Coolermaster HAF 922 case. The mainboard died, so I tried
to put a spare board into it. That is GA-H55M-S2V. According to the
sticker on the box, it is micro ATX form factor.
The manual for the HAF 922 says it takes ATX or micro ATX but it does
not have a standoff position for one of the holes on the mainboard.
I suspect Coolermaster is at fault. I have a Silvestone case similar
size to the HAF, and it has lots of possible standoff holes.
The board comes in different versions (revisions).
I found a picture of one here.
http://www.gigabyte.pl/products/mb/specs/ga-h55m-s2vrev_14.html
Dimensions are 244mm x 210mm. A full-sized MicroATX would be
244mm x 244mm. Or 9.6" x 9.6". The board is a little short
of that on one dimension. On some motherboards, when
you shorten the motherboard like that, you lose a row of
mounting holes. A really narrow motherboard can be
7" on the narrow dimension, which gives poor mechanical support.
The picture of the motherboard on the page above, shows an attempt
at a full matrix.
If we look at the following doc (page 10), the holes have letter
names. Your board is missing "M", which is a little weird. Instead,
I see a target or "prime manufacturing hole" on that corner of the
board. That is used as an alignment target by things like
pick and place machines, so the components are positioned
at the correct coordinates when the board is populated at
the factory. They could have put the target in the diametrically
opposite corner of the motherboard, and run it through the
line backwards. Which would have preserved "M".
http://formfactors.org/developer/specs/matxspe1.2.pdf
The board is missing "S", because "S" conflicts with a
chip heatsink. So they just removed "S".
As to how much of an issue such changes cause, you
look at the board and see which "insertion actions"
need mechanical support underneath. Inserting or
removing a DIMM, uses "H" and "J" for support. Inserting
the main power cable, uses "L" for support. The SATA
connectors are poorly supported, but then, the standard
does not have a mounting point in that corner. The introduction
of an array of SATA connectors, came well after microATX
was invented. So "L" is called on for that edge.
It's not a total disaster as a design. I've seen full ATX
motherboards, with K,L,M missing, and then the user needs
to place insulating materials under that edge of the board,
to provide support. Apparently you got an "L" with your
slightly-small board, so it's not a complete disaster.
Just insert the screws, where you can.
If the motherboard tray was missing "L", then that would
be an unfortunate mix of design decisions. And then you would
be advised to cook up a solution for it. To add some support,
to prevent damage to the motherboard.
Paul
