Hardware Reference
In-Depth Information
on the module that act as an interface between the actual RAM chips and the chipset. The
registers temporarily hold data passing to and from the memory chips and enable many
more RAM chips to be driven or otherwise placed on the module than the chipset could
normally support. This allows for motherboard designs that can support many modules
and enables each module to have a larger number of chips. In general, registered modules
are required by server or workstation motherboards designed to support more than four
sockets. One anomaly is the initial version of the AMD Athlon 64 FX processor, which
alsousesregisteredmemorybecauseitsSocket940designwasbasedontheAMDOpter-
onworkstationandserverprocessor.SubsequentSocket939,AM2,andSocketFversions
of the Athlon FX no longer require registered memory.
To provide the space needed for the buffer chips, a registered DIMM is often taller than a
standard DIMM.
Figure 6.10
compares a typical registered DIMM to a typical unbuffered
DIMM.
Figure 6.10
A typical registered DIMM is taller than a typical unbuffered DIMM to provide room for buf-
fer chips.
Tip
If you are installing registered DIMMs in a slimline case, clearance between the top of the
DIMM and the case might be a problem. Some vendors sell low-profile registered DIMMs
that are about the same height as unbuffered DIMMs. Use this type of DIMM if your system
