Evaluation of soft-core processors on a Xilinx Virtex-5 field programmable gate array. Page: 11 of 37
This report is part of the collection entitled: Office of Scientific & Technical Information Technical Reports and was provided to Digital Library by the UNT Libraries Government Documents Department.
The following text was automatically extracted from the image on this page using optical character recognition software:
The purpose of this document is to provide an evaluation of soft core processors within a Xilinx
Virtex-5 FX field programmable gate array (FPGA). The intent of this report is to provide a
baseline comparison on these soft-core processors without making modifications to the
processors themselves and only using the tools and netlists provided. The performance and
capability of each processor and the trade-offs that each provides is discussed within this
Node-based architecture (NBA) designs for future satellite projects hold the promise of
decreasing system development time and costs, size, weight, and power and positioning the
laboratory to address other emerging mission opportunities quickly. FPGA-based modules will
comprise the core of several of the NBA nodes. Microprocessing capabilities will be necessary
with varying degrees of mission-specific performance requirements on these nodes. To enable
the flexibility of these reconfigurable nodes, it is advantageous to incorporate the microprocessor
into the FPGA itself. Three reconfigurable FPGA-based soft-core processors for use in future
NBA systems were evaluated on the Xilinx Virtex-5 FX-70T FPGA; the MicroBlaze (uB), the
open-source Leon3, and the licensed Leon3. The licensed core is also referenced as the
Leon3FT because it was designed to be fault-tolerant within an Actel RTAX FPGA. The
licensed Leon3 used within this evaluation was not intended to be fault-tolerant in a Xilinx
device, but to use as a prototype and develop with an equivalent netlist on a reconfigurable
platform rather than with the complications of developing on an OTP platform.
To evaluate the different soft-core processors, two performance benchmark applications were
used. The first application used was the Dhrystone benchmark, which is used for fixed-point
operation metrics. The second application used was the Whetstone benchmark, which is used for
single-precision floating-point operation metrics. Each processor was tested under varying
configurations such as enabling or disabling the cache. The FPGA resource utilization for each
processor was also recorded for each configuration.
The results show that enabling the cache and the floating-point unit (FPU) greatly improves
processor performance. With the cache disabled, though, the Leon was more efficient than the
uB while running out of external memory, but the performance was still low. With cache
enabled, the performance on both processors increased by about a factor of 20. With the FPU
enabled, the uB performance increased by a factor of 40, while the Leon's performance increased
by a factor of about 400 to 1000.
The Leon3 uses more resources than the uB when utilizing the FPU. The FPU used within the
Leon3 is designed to be a more capable hardware instantiation than the uB FPU; thus, the extra
resources needed. For example, the Leon3 FPU can handle double-precision floating-point
operations whereas the uB FPU cannot. With only the cache enabled, each processor utilized
about the same number of resources. With the cache and FPU disabled, both processors used
about the same number of resources.
Here’s what’s next.
This report can be searched. Note: Results may vary based on the legibility of text within the document.
Tools / Downloads
Get a copy of this page or view the extracted text.
Citing and Sharing
Basic information for referencing this web page. We also provide extended guidance on usage rights, references, copying or embedding.
Reference the current page of this Report.
Learn, Mark Walter. Evaluation of soft-core processors on a Xilinx Virtex-5 field programmable gate array., report, April 1, 2011; United States. (https://digital.library.unt.edu/ark:/67531/metadc836670/m1/11/: accessed May 24, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.