Updated spice2x features (markdown)

spice2x-features.md

@@ -249,6 +249,7 @@ Spice API is also available over the serial port (`-apiserial` and `-apiserialba
     * e.g., `spice64.exe -exec bm2dx.dll -modules modules` causes game to launch bm2dx but without I/O emulation or IIDX-specific hooks.
     * If you still need to enable things selectively, you can specify `-io` to enable all I/O hooks again, only enable partial I/O emulation using things like `-acio` `-icca` `-device` `-extdev` `-sciunit`, or the game specific hooks (e.g., `-iidx`, `-sdvx`).
     * There are also other options such as `-devicehookdisable` which may be needed.
+    * This is typically used on arcade cabinets (cabs). However, if you only have partial I/O, the options may not be granular enough.
 
 ## Bonus features for games