DSP Performance in Stratix II GX Devices
Stratix® II GX devices, which feature dedicated digital signal processing (DSP) block circuitry offer higher data processing capacity and are more flexible and cost-effective than discrete DSP processors. DSP processors typically have up to eight dedicated multipliers, whereas Stratix II GX devices offer up to 252 18x18 dedicated multipliers and additional logic element (LE)-based multipliers.
Stratix II GX devices are the ideal choice for implementing algorithms that greatly benefit from the large number of multipliers in Stratix II GX devices, such as finite impulse response (FIR) filters, forward error correction (FEC), modulation-demodulation, and encryption.
Further, with the availability of software tools such as the Altera® DSP Builder (an interface between the Quartus® II software and The MathWorks' MATLAB/Simulink tool), Stratix II GX devices can be used to implement entire DSP systems such as RAKE receivers and W-CDMA transmitters.
Higher Data Throughput
Each DSP block in Stratix II GX devices contains eight 9-bit x 9-bit multipliers, which are capable of running at 450 MHz. Therefore, each DSP block provides data throughput of 3.6 giga multiply-accumulates per second (GMACS). Each DSP blocks can also be configured as 18-bit x 18-bit multipliers. The largest Stratix II GX device, EP2SGX130, offers 63 DSP blocks that can perform up to 252 18-bit x 18-bit parallel multiplications and provide a combined data throughput of up to 113.4 GMACS. This is over 40 times more DSP throughput than traditional DSP processors.
In addition to the embedded multipliers available in DSP blocks, TriMatrixTM memory can be used as soft multipliers that are based on a look-up table (LUT) implementation of multiplication operation. Soft multipliers also support distributed arithmetic functions that provide optimal resource balance between memory and LE utilization of several DSP algorithms such as FIR filters. Soft multipliers extend the DSP bandwidth available in Stratix II GX DSP blocks by 300 percent.
Using ALMs to Implement Multipliers
For very multiplication-intensive applications, Stratix II GX devices can implement additional multipliers and DSP functions using adaptive logic modules (ALMs). For multiplication operations, partial products are generated and then summed together. A Stratix II GX FPGA can implement the partial product in the 4-input LUT in front of the full adder in the same ALM. In the partial products summation step, the 3-input adding feature of a Stratix II GX device significantly compresses the number of add stages which allows for improved performance and less logic usage.
The different DSP features in the Stratix II GX FPGA can be used for implementing performance-critical DSP functions in hardware. These functions would otherwise consume much of the DSP processor's processing power, thereby slowing down the overall system performance. Stratix II GX devices can be used as FPGA co-processors in DSP systems.
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