With the introduction of the Stratix® II FPGA family came the first revolution in high-performance FPGA architectures in several years—the adaptive logic module (ALM). Since then, all high-density Stratix series FPGA families have utilized the ALM structure and all of the benefits it brings. The Alms are routed with the MultiTrack interconnect architecture, enabling a Stratix series FPGA to implement high-speed logic, arithmetic, and register functions. The Alms are fully integrated in Quartus® II development software to easily deliver the highest performance, highest logic utilization, and lowest compile times.
For more details on the Stratix and Stratix GX FPGA architectures see the respective handbook chapters.
The key to high performance in a Stratix series FPGA is the area-efficient ALM. It has 8 inputs with a fracturable look-up table (LUT) that can be divided into two adaptive LUTs (ALUTs) using Altera's patented LUT technology. Each ALM is capable of implementing:
- A full 6-input LUT or select 7-input LUT
- Two independent outputs of multiple combinations of smaller LUT sizes for efficient logic packing
- Complex logic-arithmetic functions without additional resources
Figure 1 and Table 1 outline the structure and features of valid configurations available within the ALM.
Figure 1. ALM Structure
| Table 1. ALM Features and Advantages | |
|
Available Resources per ALM |
Advantages |
|---|---|
| 8-Input Fracturable LUT |
|
| Two Embedded Adders |
|
| Two Registers |
|
| Two Outputs |
|
| MLAB |
|
Refer to the Logic Array Blocks and Adaptive Logic Modules (PDF) chapter of the Stratix IV Device Handbook for more information.
The MultiTrack Interconnect
High-performance Stratix series FPGAs leverage the MultiTrack interconnect technology. This technology consists of continuous, performance-optimized routing lines of different lengths used for communication within and between distinct design blocks.
The MultiTrack interconnect technology, shown in Figure 2, is used in Altera's Stratix FPGA series to:
- Provide the industry's best connectivity with up to five times the logic in a single hop (compared to the competition)
- Provide more accessibility to any surrounding LAB with much fewer connections, thus improving performance and reducing power
- Avoid area congestion to provide better logic packing
Figure 2. Stratix FPGA Series MultiTrack Interconnect Connectivity
Advantages of Altera's High-Performance FPGA Architecture
The fracturable LUT, two full adders, two registers, and additional logic enhancements that enable the ALM to be partitioned into two independent LUTs for maximum efficiency make Stratix series FPGAs the fastest and biggest FPGAs in their respective class—with no wasted logic.
