The Xilinx Virtex-5 FPGA family was unveiled in 2006, providing new levels of capability through 65nm process technology along with novel architectural enhancements. Virtex-5 cemented Xilinx’s technology leadership for years following its introduction.
Virtex-5 implemented numerous innovative features including embedded processors, high-speed serial I/O, advanced clocking and power management techniques. These came together to enable a giant leap in bandwidth, efficiency and ease-of-use compared to prior Virtex generations.
This article will dive into the key innovations of Virtex-5 to understand what made it a milestone in FPGA history and a popular choice for high-performance applications. Comparison to predecessor and successor families is also provided for context.
Virtex-5 FPGA Family Overview
The Virtex-5 family consists of seven platforms tailored to different application needs:
- LXT – High performance logic
- SXT – Signal processing
- TXT – High IO bandwidth
- FXT – Low power
- HXT – Automotive
- QXT – Military qualified
- CXT – Commercial space ready
With up to 8 billion transistors and gate counts up to 2 million, Virtex-5 was the most capable FPGA when introduced.
Some of the common features across Virtex-5 platforms include:
- 65nm process technology
- Embedded PowerPC processors
- High speed serial transceivers up to 11.2Gbps
- Advanced clock management techniques
- Enhanced DSP48E slices
- Multi-gigabit memory bandwidth
Let’s look at some of the major innovations driving Virtex-5’s leadership performance.
65nm Process Technology
The Virtex-5 family leveraged a high-performance triple-oxide 65nm manufacturing process with nine layers of copper interconnects. This enabled much higher logic density, performance and lower power consumption compared to previous 90nm nodes.
Some of the benefits of 65nm technology include:
- 2X logic capacity over preceding Virtex-4 generation
- Faster transistors enabling 30% higher speed or 25% lower power
- 1.2V core voltage resulting in significant power savings
- Tighter design rules producing smaller die sizes
The 65nm node gave Xilinx a multi-year competitive advantage in achievable FPGA gate density. Smaller feature sizes also facilitated including abundant hard IP blocks.
A major innovation in Virtex-5 was the introduction of PowerPC 440 embedded cores directly within the FPGA fabric. Key features:
- Up to 8 processor cores per device
- PowerPC architecture with high performance 32-bit RISC execution
- Floating point unit integrated in each core
- 32KB L1 caches for instructions and data
- Hardware debug capability
Embedding PowerPC 440 cores eliminated the need for external processors in many applications. This simplified system development by enabling single-chip solutions encompassing both hardware and software programmability.
High Speed Serial Transceivers
To keep pace with rapidly evolving serial interconnect standards, Virtex-5 incorporated up to 1,040 high speed serial transceivers supporting data rates up to 11.2Gbps.
Key enhancements included:
- Multi-rate capability from 155Mbps to 11.2Gbps
- Sophisticated equalization techniques like CTLE and DFE
- Low power modes for 10G operation under 5W per channel
- Support for 10G Ethernet, Fibre Channel, RapidIO and Interlaken
High speed serial connectivity enabled designers to harness the bandwidth needed for high throughput applications.
Advanced Clock Management
Efficient clocking schemes are critical for large FPGAs like Virtex-5. Key clocking capabilities include:
- Digital clock managers (DCMs) – flexible frequency synthesis, deskew and jitter filtering
- Mixed-mode clock managers (MMCM) – high-performance PLL-based clocking with low jitter
- 16 low-skew global clock networks – distribute clocks across large device
- Zero-delay buffers – clean clock signals throughout FPGA
- Per-pin programmable clocking – customize each IO pin’s clocking
Robust clock management was critical to utilize Virtex-5’s high logic capacity for complex synchronous systems.
Enhanced DSP48E Slices
To accelerate digital signal processing tasks, Virtex-5 upgraded the DSP slice architecture. DSP48E enhancements included:
- 25 x 18 bit multipliers
- 48-bit adder/accumulator/register units
- Cascading for wide precision math
- Pipelining and overflow handling
- Bitwise logical capabilities
DSP48E slices provided both high performance and flexibility for math-intensive algorithms mapped into the FPGA fabric.
Multi-Gigabit External Memory Bandwidth
Large on-chip memories through block RAMs were augmented by multi-gigabit external memory interfaces.
Key features included:
- DDR, DDR2 and DDR3 memory controllers
- Up to 4 memory interfaces with sustained bandwidth over 20 Gbps
- Multi-port modes supporting concurrent access
- Error detection and correction logic
- Interfaces optimized for low latency
Abundant external memory bandwidth enabled building high performance memory subsystems inside Virtex-5 FPGAs.
Power Management and Savings
To optimize energy efficiency, Virtex-5 incorporated both architectural and process enhancements for lower power. These encompassed:
- Triple-oxide leakage reduction in 65nm process
- FPGA-wide power gating for inactive block shutdown
- Clock gating and disabling for unused logic
- Hibernation mode for extreme low static power
- Multi-threshold voltage selection for performance tradeoffs
- Advanced simulation for power analysis and optimization
Lower power expanded Virtex-5’s applicability in thermally and energy constrained application spaces.
Design Flow and IP Support
To assist designers in harnessing Virtex-5’s rich capabilities, Xilinx offered extensive design tools and IP support:
- ISE Design Suite – RTL synthesis through device programming
- EDK – Embedded software development
- System Generator – DSP design entry and simulation
- Platform Studio – SOC design creation
- AccelDSP – DSP algorithm synthesis
- Core Generator – parametrizable IP modules
- Reference designs – optimized example implementations
This comprehensive toolchain enabled designers to fully tap into Virtex-5 performance and functionality.
Conclusion on Virtex-5 Innovations
Through its 65nm manufacturing, abundant hard IP blocks, high speed IOs and advanced power management, Virtex-5 represented the state-of-the-art in FPGA technology for its time. It extended Xilinx’s market dominance in high-end FPGAs through a combination of architectural enhancements layered atop leading-edge process technology.
Virtex-5 vs. Virtex-4 Comparison
To appreciate the generational advancements Virtex-5 delivered, it is instructive to compare against the previous generation Virtex-4 family.
We can see Virtex-5 demonstrated advances across all resource types while incorporating fully embedded processors. This combination cemented Virtex-5’s standing as the premium high-capability FPGA at the 65nm node.
Virtex-5 vs. Virtex-6 Comparison
Virtex-6 was the successor to Virtex-5, migrating to a 40nm manufacturing process with architectural enhancements.
Some key differences between Virtex-5 and Virtex-6 include:
- 65nm process
- PowerPC 440 cores
- Up to 1,040 high speed transceivers
- DSP48E slices
- Higher cost per gate
- 40nm process enabling 2X capacity
- Enhancements like integrated PCIe blocks
- Low power 40Gbps transceivers
- Advanced DSP48E1 slices
- Lower cost per gate
While Virtex-6 pushed FPGA technology further, Virtex-5 continued to maintain its place in applications not requiring maximum capacity or bandwidth but needing significant DSP resources. The two families nicely coexisted throughout their lifespans.
Virtex-5 FPGA Applications
Thanks to its high performance fabric, abundant DSP slices and hard IP for functions like processing and high speed IO, Virtex-5 excelled in diverse applications including:
- Wireless base stations
- High definition video processing
- Medical and scientific computing
- Test and measurement
- Image processing
- Radar and sonar
- High energy physics
- Military and aerospace
- Broadcast infrastructure
- Cryptography and network security
For compute and data-intensive applications, Virtex-5 offered unmatched capability compared to alternatives like ASICs or ASSPs which lacked hardware programmability.
Virtex-5 sales eventually topped $5 billion as Xilinx dominated the high-end FPGA space throughout its successful multi-year lifespan.
Virtex-5 FPGA FAQ
Here are some frequently asked questions about the Virtex-5 FPGA family:
Q: What was the largest Virtex-5 FPGA device available?
A: The XC5VSX240T containing over 2 million logic cells was the highest capacity Virtex-5 FPGA.
Q: Did all Virtex-5 FPGAs include embedded PowerPC cores?
A: No, the lower cost LX sub-family did not incorporate PowerPC cores. All other Virtex-5 families had embedded processors.
Q: How much on-chip block RAM did Virtex-5 FPGAs provide?
A: Virtex-5 had between 4.5Mb and 51Mb of block RAM depending on device size, among the highest in any FPGA at the time.
Q: What was the typical core voltage for Virtex-5 operation?
A: Virtex-5 operated at 1.0 – 1.2V core voltage enabling significant power savings versus predecessor 90nm FPGAs.
Q: Which manufacturing process came after 65nm used for Virtex-5?
A: Virtex-6 transitioned to a 40nm process followed by 28nm for Virtex-7 achieving even higher density and performance.
In conclusion, the Virtex-5 FPGA family represented a major milestone for programmable logic capability and efficiency. Its 65nm manufacturing, hard IP integration and high speed serial I/O enabled Xilinx to cement its leadership through a combination of cutting-edge process technology and architectural enhancements.
Virtex-5 provided a 2X generational jump versus Virtex-4 across all resource types while incorporating novel elements like embedded PowerPC processors. This combination of advances resulted in Virtex-5’s broad adoption across applications needing high density, bandwidth and DSP performance.
Xilinx’s technical leadership and execution with Virtex-5 maintained its dominance in high-end FPGAs for years and further propelled the company’s rapid growth in the 2000’s. The innovations in Virtex-5 illustrate how Xilinx consistently pushed programmable logic boundaries with each successive product generation.