The differences in frequency coverage and timing precision between the GBT and CHIME / Pulsar data sets lead to observable differences in their DM measurements . In particular , while the GBT data yield superior RMS timing residuals in both receiver bands than those obtained with CHIME / Pulsar , the CHIME / Pulsar data nonetheless yield better precision in DM measurements ; the median uncertainty in GBT DMs determined with PulsePortraiture is ∼ 8 × 10 −4 pc cm −3 , while the same measure in the CHIME / Pulsar data set is ∼ 2 × 10 −4 pc cm −3 . The median DMX measurement uncertainty in the CHIME / Pulsar era has comparable precision to that obtained with GLOW by Donner et al . ( 2020 ) , ∼ 4 × 10 −5 pc cm −3 . Further analysis of the DM timeseries for PSR J0740 + 6620 will be the subject of future works .