[new 16 August 2007]

In theory there is no limit to the number of tiles you can stack on top of each other. In Logic Tiles the functionality of the signals routed between the tiles is not defined, and there is no signal rotation in the stacking headers.

There is a real limit for the number of tiles you can stack together, which mainly depends on:

• The maximum load of the signals connected to several tiles (e.g. CLK_GLOBAL)
• The maximum delay of the signals routed up and down the stack
• The minimum speed of your design
• The maximum power that can be supplied by the baseboard

Many users have been able to stack up to 4 Logic Tiles on top of an EB rev D or PB926EJ-S rev E baseboard, but this depends on the constraints above.