> 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. The SX95T is available for a reasonable price (~$2795.00), so I will go with those. Do you have an exact part number for that chip? Just for fun I priced an SX240 that's considered for roach-II. They're $15,500 each! Still cheaper than a BEE-2, though... John > > 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 >> >
