EP2S90F1020C4N Datasheet, PDF (18/238 Pages) Altera Corporation – The Stratix II family offers the following features

Adaptive Logic Modules
synchronous load, and clock enable control for the register. These LAB-
wide signals are available in all ALM modes. See the “LAB Control
Signals” section for more information on the LAB-wide control signals.
The Quartus II software and supported third-party synthesis tools, in
conjunction with parameterized functions such as library of
parameterized modules (LPM) functions, automatically choose the
appropriate mode for common functions such as counters, adders,
subtractors, and arithmetic functions. If required, you can also create
special-purpose functions that specify which ALM operating mode to use
for optimal performance.
Normal Mode
The normal mode is suitable for general logic applications and
combinational functions. In this mode, up to eight data inputs from the
LAB local interconnect are inputs to the combinational logic. The normal
mode allows two functions to be implemented in one Stratix II ALM, or
an ALM to implement a single function of up to six inputs. The ALM can
support certain combinations of completely independent functions and
various combinations of functions which have common inputs.
Figure 2–7 shows the supported LUT combinations in normal mode.
2–10
Stratix II Device Handbook, Volume 1
Altera Corporation
May 2007