Hardware Reference
In-Depth Information
Form factor
Like cases, motherboards are available in numerous form factors, the
most popular of which are full ATX, μATX, and Mini-ITX. Although Mini-
ITX motherboards are physically compatible with μATX and ATX cases
and μATX motherboards with ATX cases, it seldom makes sense to install
a smaller form factor motherboard in a larger case. A μATX motherboard
generally costs about as much as a similar full ATX motherboard, and Mini-
ITX motherboards are often actually more expensive than similar μATX
and ATX boards. Using a smaller motherboard than the case can accept
simply gives up memory and expansion slots, communications ports, and
other potentially valuable features for no reason. It may also cause prob-
lems with cables that are too short to reach the smaller motherboard.
Memory slots
Every motherboard includes one or more memory slots, but the number
and type of these slots differ, as follows:
Number
Typical ATX motherboards provide slots for four memory modules.
μATX boards usually provide two or four slots. Mini-ITX boards pro-
vide one or two slots. All other things being equal, it's better to have
more memory slots than fewer, for three reasons. First, the number of
memory slots (and the maximum capacity of each) puts a hard limit
on the amount of memory that can be installed. Second, it may be
less expensive—sometimes much less expensive—to install a given
amount of memory using more smaller modules rather than fewer
larger modules. For example, if you intend to install a total of 8 GB of
memory, the price of four 2 GB memory modules may be much less
than the price of two 4 GB modules. Third, if you decide to upgrade
your system in mid-life, it's easier and cheaper to add memory mod-
ules than to remove and discard the current modules and replace
them with all new modules.
Type and capacity of modules supported
Current desktop motherboards use one of four types of memory
modules: 240-pin DDR2-SDRAM DIMM, 240-pin DDR3-SDRAM DIMM,
200-pin DDR2-SDRAM SO-DIMM, or 240-pin DDR3-SDRAM SO-DIMM.
The SO-DIMM modules are actually notebook memory, but they are
used by a few Mini-ITX motherboards. Mainstream ATX, μATX, and
Mini-ITX motherboards accept either 240-pin DDR2 or DDR3 DIMMs.
A few hybrid Socket AM2+/AM3 motherboards accept
either
240-pin
DDR2
or
DDR3 DIMMs, but only one type at a time.
Just because a memory slot physically accepts a memory module
doesn't mean that module is compatible with that motherboard. The
chipset and/or BIOS may limit the module capacity. For example, al-
though a 4 GB DDR2-SDRAM module may be physically identical to a
2 GB module, a particular motherboard may support 2 GB modules,
but not 4 GB modules. If you install the 4 GB module, the results are
unpredictable. The system may fail to boot. More likely, it will boot
normally, but will recognize the 4 GB module as only 2 GB. If the BIOS
