Appendix E
Modifying and Installing I/O Expansion Boards
© National Instruments Corporation
E- 3
VXIpc -850 Series User Manual
Because larger DRAM sizes may employ taller SIMMs, you must be
careful that the component height of the PCI board does not interfere
with the SIMMs in such a way that electrical shorts occur or that the
PCI board is stressed enough to compromise its physical or electrical
integrity.
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 will interfere with the circuit card of the plug-in board . Most
SIMM modules are at least one inch in height and would extend into
the plane of the ISA circuit card by 0.15 in. Therefore, National
Instruments does not recommend the use of cards that are greater than
7.72 in. in length. They can be made to fit; however, care must be taken
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 on ISA cards for the
VXIpc-850.
ISA Board
Heat Sink
Support Brackets
SIMMs
7.72 in. max
Riser Card
Front Panel
VXI Connector
Figure E- 3. Length Restrictions on ISA Plug-In Boards
