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Appendix E Modifying and Installing I/O Expansion Boards
© National Instruments Corporation E-3 VXIpc 800 Series User Manual
Length of ISA Plug-In Boards
Because ISA boards mount with the components facing away from the
CPU card, which contains the processor and system RAM, tall DRAM
SIMMs may interfere with the circuit card of the plug-in board. Most
SIMM modules are at least 1 in. high and would extend into the ISA
circuit card keepout area. Therefore, National Instruments provides
SIMMs of 0.85 in. high, and does not recommend the use of cards that
are longer than 7.72 in. if you choose to use taller SIMMs. They can be
made to fit; however, take care to ensure the following conditions:
• Contact of the board with the SIMMs should not cause electrical
shorts (because of through-hole component leads on the side of the
plug in board that contacts the SIMMs).
• Contact of the board with the SIMMs does not cause physical stress
to the plug-in board.
• Contact of the board with the SIMMs does not cause physical stress
to the riser board into which the plug-in board is inserted.
Figure E-3 shows the length restrictions for ISA cards for the
VXIpc-850 when tall SIMMs are used.
Figure E-3.
Length Restrictions for ISA Plug-In Boards Used with the VXIpc-850
when SIMMs Taller than 0.85 in. are Used
ISA Board
Heat Sink
Possible Support
Bracket Positions
1.0 in. High
SIMMs
7.72 in. max
Riser Card
Front Panel
VXI Connector