Hardware Reference
In-Depth Information
Memory Banks
Memory chips (DIPs, SIMMs, SIPPs, and DIMMs) are organized in banks on mother-
boards and memory cards. You should know the memory bank layout and position on the
motherboard and memory cards.
You need to know the bank layout when adding memory to the system. In addition,
memory diagnostics report error locations by byte and bit addresses, and you must use
these numbers to locate which bank in your system contains the problem.
The banks usually correspond to the data bus capacity of the system's microprocessor.
Table 6.13
shows the widths of individual banks based on the type of PC.
Table 6.13 Memory Bank Widths on Various Systems
DIMMsareidealforPentium(andhigher)systemsbecausethe64-bitwidthoftheDIMM
exactly matches the 64-bit width of the Pentium processor data bus. Therefore, each
DIMM represents an individual bank, and these can be added or removed one at a time.
Many recent systems have been designed to use matched pairs or triples of memory mod-
ules for faster performance. So-called “dual-channel” and “tri-channel” designs treat two
or three matched modules as a single bank of memory.
The physical orientation and numbering of the SIMMs or DIMMs used on a motherboard
are arbitrary and determined by the board's designers, so documentation covering your
system or card comes in handy. You can determine the layout of a motherboard or an ad-
apter card through testing, but that takes time and might be difficult, particularly after you
have a problem with a system.
