Module Connectors
Over the years, the connectors on the edge of SIMM and DIMM modules and the connec-
torsinsidetheirmountingsocketshavebeenmadefromeithergoldortin.Theconnectors
on a SIMM and its socket are available in either gold or tin and DIMMs use only gold for
both. Older SIMMs also used gold, but most newer SIMMs now use tin. These two metals
should not be mixed, which means that a tin SIMM connector should not be inserted into
a gold SIMM socket, and vice versa. Mixing these metals can cause a chemical reaction
thatcausestinoxidetogrowonthegoldandpossiblycreateanunreliable,anddifficultto
diagnose, electrical connection.Matching Memory to the Motherboard
The memory added to a system, whatever its packaging, must be matched to the width of
the data bus of the motherboard. Any data transferred to the CPU, to cache memory, or
to the peripheral devices on a PC, moves over the data bus. The width of the data bus
(alsoreferredtoasitscapacity)ismeasuredinbits.Thedatabuswidthalsorepresentsthe
amount of data that can flow over it in one clock cycle. The primary reason for memory
banks on a motherboard is to arrange the memory in sets that take advantage of the bus
width to transfer data. A memory bank holds enough memory so that the width of the
memory matches that of the data bus.(^140) PC Hardware: A Beginner’s Guide
Figure 7-6. A DIMM memory module