processor-to-logic latency, AXI link: one board, the engine at its measured clock
  timer: CNTVCT_EL0 at 99.999 MHz, one tick 10.0 ns
  the timer alone (two reads, an ISB each)                   median      10 ns  p10      10  p90      20  p99      20  max       20  mean      11  (n 20000)
  EMIO signature read (a processor GPIO register)            median     230 ns  p10     230  p90     240  p99     240  max    89851  mean     237  (n 100000)
  AXI-Lite read, a link register                             median     230 ns  p10     230  p90     230  p99     230  max    19920  mean     233  (n 100000)
  AXI-Lite read, an engine register                          median     240 ns  p10     240  p90     240  p99     240  max    25680  mean     242  (n 100000)
  a DSB alone                                                median      10 ns  p10      10  p90     110  p99     150  max    10470  mean      28  (n 100000)
  AXI-Lite write and its response (DSB), a link register     median     250 ns  p10     250  p90     350  p99     380  max    22460  mean     269  (n 100000)
  AXI-Lite write and its response (DSB), an engine register  median     250 ns  p10     250  p90     350  p99     380  max    56791  mean     269  (n 100000)
  AXI-Lite writes back to back, no DSB between: 51 ns each over 100000
  AXI-Lite write then read (select a cell, read its field)   median     460 ns  p10     460  p90     580  p99     600  max    53021  mean     481  (n 100000)
  guarded read, as every job access goes (signature, then read) median     470 ns  p10     460  p90     470  p99     470  max    21530  mean     470  (n 100000)
  a 1-entry write list by DMA, kick to done (4 writes, polls) median    7640 ns  p10    7570  p90    7790  p99    9340  max    25820  mean    7775  (n 5000)
  a 512-entry write list by DMA (one page), kick to done     median   20310 ns  p10   20010  p90   20480  p99   23510  max    54711  mean   20433  (n 2000)
    = 39.7 ns an entry, 25.2 M register writes/s
  128 chains' results written back (one page), kick to read  median   37550 ns  p10   37240  p90   37990  p99   47880  max    49670  mean   37825  (n 2000)
    = 293 ns a chain
  AXI, DMA and sequencer: a full table (64 levels x 128 fields, 32835 register writes): median 3.81 ms of 6, 116 ns a write
  AXI, DMA and sequencer: 65536 chains of 8 cells x 4 sweeps: 0.285 s, 4.34 us a chain, 230153 chains/s
  AXI, plain register accesses: a full table (64 levels x 128 fields, 32835 register writes): median 17.46 ms of 6, 532 ns a write
  AXI, plain register accesses: 16384 chains of 8 cells x 4 sweeps: 0.154 s, 9.42 us a chain, 106113 chains/s
  AXI accesses 1174977, DMA lists 8862, sequencer batches 257, write-backs 2714