Hi Michael, Hmmm. Can you link the repo you're using and a reference design?
Thanks Jack On Sun, 18 Sep 2016 at 15:05 Michael D'Cruze < michael.dcr...@postgrad.manchester.ac.uk> wrote: > Hi Jack, > > > > To implement the change in optimisation I altered the delay_bram init > script. Line 84 which configures the Xilinx ram block, I changed the > parameter ‘optimize’ from ‘Area’ to ‘Speed’. No other changes were made, > so, I think this is the former case? > > BW > Michael > > > > *From:* Jack Hickish [mailto:jackhick...@gmail.com] > *Sent:* 18 September 2016 22:27 > *To:* Michael D'Cruze; casper@lists.berkeley.edu > *Subject:* Re: [casper] Spectrum woes > > > > Hi Michael, > > > > Is this actually the optimisation parameter of the xilinx bram block, or > an optimisation of a casper block which completely changes some underlying > circuit (eg by doing a bunch of fanout control and instantiating multiple > small brams instead of one big one)? > > If the latter, are you sure it's not a bug in the casper implementation? > Perhaps a mismatch of latency on various things being fanned out? > > > > Trust nothing. > > > > Jack > > > > On Sun, 18 Sep 2016 at 14:21 Michael D'Cruze < > michael.dcr...@postgrad.manchester.ac.uk> wrote: > > Dear all, > > > > I’ve been chasing the cause of some nasty artefacts in my spectra > recently. The first turned out to be a known bug in the Xilinx compiler, > activated when the BRAM_sharing optimisation in the FFT is checked, however > the artefacts I’m seeing since seem to be activated by the RAM blocks in > the delay_bram block being configured for “Speed”, and not the default > “Area”. > > > > Below are links to two spectra. They were both recorded from the Lovell > telescope’s L-band receiver while the telescope was pointing at the zenith. > The logic used in both cases is identical, with the exception that the > delay_brams in the first spectra are configured for Speed, and in the > second they are configured for Area (default). All operating parameters > were the same in both cases. > > > > https://dl.dropboxusercontent.com/u/38103354/figure_1.png > > https://dl.dropboxusercontent.com/u/38103354/r13a_libs_18-09_2207.PNG > > > > Aside from how ugly the first spectrum looks (there are signals in there > which simply don’t exist), even the accumulated power is different. The > vertical scale is logarithmic so this is a factor 100 or so higher with the > brams configured for Speed. I don’t understand how they could be so > different, nor why configuring the brams for Speed should make any > difference at all, not least a difference of this magnitude. > > > > The most worrying thing for me now is that configuring the brams for Speed > was key to getting my larger designs (16k and 32k channels) to meet timing. > If I need to reconfig for Area, I’m going to have to brawl with Par and > PlanAhead all over again… It actually took a few goes to get just that 4k > channel design to compile. > > > > I’d appreciate ideas/suggestions! > > Thanks > > Michael > > > > > >
