This paper describes the Altera Stratix II™ logic and routing architecture. This architecture features a novel adaptive logic module (ALM) that is based on a 6-LUT, but can be partitioned into two smaller LUTs to efficiently implement circuits containing a range of LUT sizes that arises in conventional synthesis flows. This provides a performance increase of 15% in the Stratix II architecture while reducing area by 2%. The ALM also includes a more powerful arithmetic structure that can perform two bits of arithmetic per ALM, and perform a sum of up to three inputs. The routing fabric adds a new set of fast inputs to the routing multiplexers for another 3% improvement in performance, while other improvements in routing efficiency cause another 6% reduction in area. These changes in combination with other circuit and architecture changes in Stratix II contribute 27% of an overall 51% performance improvement (including architecture and process improvement). The architecture changes reduce area by 10% in the same process, and by 50% after including process migration.

This paper describes architectural enhancements in the Stratix-III™ and Stratix-IV™ FPGA architectures. These architectures feature programmable power management, which allows the power and performance of logic and routing to be varied to minimize total power without any performance loss. This paper describes the technique used for programmable power management, and describes the experimental evaluation that led to the choice of regions in these architectures. The memory architecture is also explored by adding heterogeneous memory mapping to the FPGA Modeling Toolkit, and used to explore LUT based memory structures. The ALM structure provides more inputs than required for a simple 6 LUT, which can be used with simple modifications to efficiently support simple dual-ported LUT based RAM. Replacing the Stratix-II™ small memory blocks with LUT RAM and changing the size of other two memories is shown to reduce overall core area across a set of benchmark designs.

This paper describes architectural enhancements in the Altera Stratix-V™ FPGA architecture, built on a 28nm TSMC process, together with the data supporting those choices. Among the key features are time borrowing flip-flops, a doubling of the number of flip-flops per LUT compared to previous Stratix architectures, a simplified embedded 20kb dual-port RAM block, and error correction that can correct up to 8 adjacent errors. Arithmetic performance is significantly improved using a fast adder with two levels of multi-bit skip. We also describe how the routing architecture and layout is optimized for the 28nm process to take advantage of a wider range of wire thicknesses offered on the different layers, and improvements in performance and routability are obtained without dramatic changes to the repeated floorplan of the logic plus routing fabric.