OP-STHRU-64 description
From embeddedTS Manuals
The option "OP-STHRU-64" includes a 64 pin PC104 connector that extends the pins so the TS-8100 does not need to be the base of the PC104 stack. This option is not required for stacking PC104 peripehral on the TS-8100 as the peripherals include a stack through connector.