Hi John, The ROACH can take the LX110T, LX155T, or SX95T. The LX series has very few multipliers, even the new LX155T only has 128, which is still fewer than on the IBOB. For sheer size of FFT, we're usually multiplier-limited. I tried building a PFB for the LX110T on the ROACH prototype and ran out of multipliers at only about 25% logic utilization.
That build was a 2^13 real PFB (2^12 complex channels) with 4 taps and 4 parallel inputs. Using 8 parallel inputs to get the full bandwidth of the ADCs, I think that dropped the design down to something like 1K channels. I think the 64 DSP48E's of the LX110T is definitely not the way to go for DSP applications. The 128 on the LX155T is a slightly better balance, but you're still losing 80% of the multipliers for a 65% increase in logic. Thanks, Henry John Ford wrote:
Hi all. What are the recommended FPGA's for the ROACH? I want the one that will allow me to build the biggest PFB/FFT's in the chip. It's not clear to me that the SX is the best one, but I really have no idea. What say you all? John
