Thanks for the info, Francois. > Hi John, > > Part numbers: > > XC5VSX95T-1FF1136C - this is the lowest speed grade, with lead, commercial > temperature range. Available today for purchase from Avnet ($2,735.00, 4 > wk > lead time) or Nu Horizons ($ 2,789.70, 22 in stock in NA). > > Lead-free is possible and the speed grade could also be a -2. -3 is not > available in SX95T (or SX240T).
Is it worth getting the -2 speed grade? It seems it may help with routing tightly packed designs, but is it necessary to run the memories and xaui links at speed? > > Does anyone have a requirement for lead-free? We (Green Bank) are leery of lead-free for long-term reliability due to the tin whisker problems. Although much of the European-built ALMA electronics is lead-free, so we shall see... John > > -Francois > > John Ford wrote: >>> 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 >>>> >> >> >> >> >
