1. UniBoard: Xilinx or Altera
Eric Kooistra
Oude Hoogeveensedijk 4
7990 AA Dwingeloo
Feb 2009
© ASTRON

2. General comparison Device ranges Device comparison Conclusion Contents
Feb 2009
© ASTRON

3. General comparison Criteria Altera Xilinx Comment Development tools
Quartus
ISE / EDK
Synthesis, softcores
Debug tools
SignalTap
ChipScope
Embedded logic analyser
MATLAB/ Simulink
DSP builder
System Generator
Generic alternatives:
- Synplify DSP
- MATLAB HDL coder
Softcore μP
Nios
Microblaze
Alternative:
- Leon (from Gaisler)
Hardcore μP -
PowerPC
Device ranges
Stratix IV
Arria II GX
Virtex 6
Spartan 6
High end range (40 nm)
Low cost range (40 nm)
Others experience
Bordeaux, Arcetri, Manchester
LOFAR, Casper, ASKAP, Nancay, Manchester
LOFAR Stratix II  Virtex 4
Keep experience on both
A general comparison shows that both Altera and Xilinx offer similar capabilities for FPGA development.
Xilinx remarks:
PowerPC 440 in Virtex5 (405 in Virtex 4)
PicoBlaze softcore for very small control
Feb 2009
© ASTRON

4. Altera - Stratix IV, 40 nm, tx/rx up to 8.5 Gbps
Device ranges
Altera - Stratix IV, 40 nm, tx/rx up to 8.5 Gbps
Xilinx - Virtex 6, 40 nm, tx/rx 3.2, 6.5 Gbps - Virtex 5, 65 nm, tx/rx 3.75, 6.5 Gbps
Only consider the newest available FPGAs.
Only consider the variants with transceivers.
Do not consider older devices:
Stratix II, 90 nm, used on LOFAR RSP2, only the GX variant has transceivers (6.375 Gbps)
Stratix III, 65 nm, do not have transceivers
Virtex 2 Pro, 130 nm, too old, transceivers can only opoerate over at most 3 m copper cable
Virtex 4, 90 nm, used on LOFAR RSP3 and TBB, only FX (with powerPC core) has transceiver (6.5 Gbps)
Only consider the newest FPGAs and those with transceivers, because:
Newest FPGA are closest to Moore’s law and offer most functionality at relatively lowest power (due to smaller nm process)
Transceivers are needed for interconnect between FPGAs and for I/O e.g. via 10 GbE
Arria and Spartan with transceivers can be interessing lower cost FPGA e.g. for interfacing an ADC to 10 GbE.
Altera low cost variants:
- Arria II GX, 40 nm, tx/rx at 3.75 Gbps - Arria GX, 90 nm, tx/rx at Gbps
Xilinx low cost variants:
- Spartan 6, 45 nm, tx/rx 3.2 Gbps
Altera availability:
Stratix IV : EP4SGX230 samples now, others consult factory
Arria GX : all buy now
Arria II GX : all contact Altera
Xilinx availability:
Virtex 5 : most buy now
Virtex 6 : samples Q2 2009
Spartan 6 : samples Q2 2009
Feb 2009
© ASTRON

5. Device comparison Criteria Stratix IV Virtex 6 Virtex 5 Comment Device
SGX230
SX315T
SX240T
SX95T
Availability
Now ?
Virtex 6 samples Q2 2009
Price
1000 $
9000 $
1700 $
Process
40 nm
65 nm
Clock MHz
540
600
550
Multiplier speed
Nof transceivers
16 (or 24) 24 16
Virtex: all on one side
Stratix: on two sides
Nof logic
91200
ALM
49500
slices
37440 slices
14720
1 ALM ≈ 0.6 – 0.9 slices
Nof multipliers
1288
1344
1056
640
Virtex: 25x18
Stratix: 18x18 (= 9x9 ?)
Block RAM
14.3 Mb
25.3 Mb
18.5 Mb
8.8 Mb
Nof IO
560
720
960
Package pins
1152
1759
1738
1136
ETH MAC
Soft core 4
Stratix IV has transceiver pins on two sides of the FPGA package, this eases PCB design. The Virtex 5 has all transceiver pins on one side of the package.
Stratix IV has devices with up to 48 transceivers.
Virtex 6 has relatively more memory and choice between more logic (LXT) instead of DSP (SXT).
Nof logic:
Xilinx defines a logic cell as 1 4-input LUT + 1 flipflop. For their largest Virtex 5 device the LX330 they state that it has 330 k logic cell and flipflops which is equivalent to k slices. A Virtex 5 slice has 4 6-input LUTs and 4 flipflops. From /(207360/4) it follows that 1 Virtex 5 slice = 6.36 logic elements. Assume that the Virtex 6 slices are equal to the Virtex 5 slices. Hence 315 k logic cells for the Virtex 6 SX315T then corresponds to about 49.5 k slices.
Note that 1 Virtex 5 slices is about two Virtex 4 slices, because it has 4 flipflops whereas the Virtex 4 slices has 2 flipflops. One ALM has 2 flipflops.
From LOFAR we found that 1 Stratix II ALM is about 1.2 Virtex 4 slices, extrapolating to Stratix IV and Virtex 5 or 6 this would imply that 1 ALM is about 0.6 slice. However Altera claims that 1 ALM is about 0.9 slice on average over a range of different designs.
Feb 2009
© ASTRON

6. Conclusion
Both Xilinx or Altera are suitable from FPGA technology and tool point of view.
40 nm for lowest power consumption: - Stratix IV EP4SGX230 is available now - Virtex 6 is expected in Q2 2009
65 nm: Xilinx Virtex 5 are available, but prices for larger FPGA are still high.
Both Altera and Xilinx have or will have “low cost” FPGA with transceivers (Xilinx: small Virtex 5, Spartan 6, Altera: Arria GX, Arria II GX)
For FPGAs with transceivers Altera Stratix IV has GX and GT (11.2 Gbps) variants, Xilinx has LXT (more logic) and SXT (more mult) variants.
For low power 40 nm about 50 % better than 65 nm.
Altera reports benchmarks and comparisons of Altera and Xilinx FPGAs and tools, which favour Altera but are not counter acted upon by Xilinx. My feeling is that in general Altera seems to be slightly better at cost, FPGA technology and tools, but not necessarily all the time.
Migration from Virtex 5 to Virtex 6 may not be trivial (e.g. board redesign).
The future looks OK for both Altera and Xilinx: - 40 nm Stratix IV, Arria II GX - 40 nm Virtex 6, Spartan 6
Feb 2009
© ASTRON