Soft-Core Processor Design - CiteSeer

• QsortInt: uses the qsort algorithm to sort 100 integers. It is equivalent to the Qsort
benchmark from the MiBench set. The only difference is the size of the dataset.
The UT Nios benchmark set also includes some test benchmarks. Test benchmarks are
sequences of assembler instructions that test the performance of specific architectural features. By
analyzing how the performance of test benchmarks depends on various parameters, it is possible
to get better insight into the performance of real applications. The test benchmarks are:
• Loops: runs a tenfold nested loop with two addition operations inside the innermost
loop, representing applications with many branches.
• Memory: performs 20 consecutive addition/subtraction operations on elements of a
one-dimensional array residing in the data memory, representing memory intensive
applications.
• Pipeline: performs a sequence of ADD, ADDI, MOV, and SUB instructions, where
each instruction uses the result of the previous instruction. The benchmark tests the
implementation of the data forwarding logic in the pipeline.
• Pipeline-Memory: performs a sequence of pairs of LD and ADD instructions, where
the ADD instruction uses the result of the LD. The benchmark tests how data
forwarding of the operands coming from the memory is implemented. Two variants of
this benchmark are used, performing the load operations from the program and data
memory. Load instructions typically access the program memory to access the
compiler generated data.
The toy and test benchmarks are run multiple times in a loop to produce reasonable run times that
can be measured.
All benchmarks were compiled using gcc for Nios (version 2.9-nios-010801-20030227)
included in the GNUPro toolkit, with the compiler optimization level 3. The time was measured
using a timer peripheral provided in the SOPC component library. The timer peripheral provides
a C library routine nr_timer_milliseconds(), which returns the number of milliseconds since the
first call to this procedure. We measure the performance in milliseconds for all benchmarks,
except for the Bitcount benchmark, whose performance is reported in bits/ms. The Bitcount
benchmark randomly generates its input dataset, so its run time varies slightly depending on the
system configuration.
5.1.2. Development Tools
The following set of cores and tools was used to obtain the results presented in this chapter.
The Altera Nios 3.0 implementation of the Nios architecture was used to compare the
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