
PC/104 and PC/104+
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the maximum achievable CPU performance of a PC/104 stack is significantly
lower than that of a desktop PC, rack-mount PC, or CompactPCI system.
Because only a few PC/104+ I/O boards are available, typical PC/104 systems
need to use ISA bus-based I/O boards. This impacts the overall system
performance since the ISA bus has a lower I/O throughput and higher latency
than the PCI bus.
I/O Expandability
Modern CPU boards usually conform to the PC/104+ standard, providing both
ISA and PCI buses for currently available. This limitation makes it very
difficult for you to build a stack that is exclusively made up of boards using the
faster PCI bus. Within a PC/104+ system, you can combine PC/104 (ISA) and
PC/104+ (PCI) boards as long as the PC/104+ boards are stacked onto the CPU
board before the PC/104 boards.
The choice of available PC/104 I/O boards is very broad and covers most I/O
types. The PC/104+ standard defines the expansion of the stack with up to
three PC/104+ (PCI) boards and up to eight PC/104 (ISA) boards. However,
because PC/104 systems are usually used for mobile controller applications,
which do not need a very high number of I/O channels, this limit is rarely
reached.
You can use the following standard I/O board form factors in a PC/104 stack
system:
• PC/104 (ISA)
• PC/104+ (PCI) — If the CPU module is a PC/104+ board
• PMC — Through a passive PC/104+ carrier board
• IP-modules — Through an active PC/104 carrier board
Advantages
The advantages of selecting a PC/104 computer for your target PC are
• Very small, ideal for mobile applications
• Rugged system, well suited for deployment in a harsh environment
• DC power operation
• Extended temperature range operation
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