RFM reads are slow. Rolf has said it should take 2-3 microseconds per read.
c1sus is taking about 7 microseconds per read, twice as slow as Rolf's claim.
The RFM card is in the IO chassis, and is sharing the PCIe bus with 4 ADC cards, 3 DAC cards, 4 BO cards, and a BIO card. Its possible this crowded bus is causing the reads to take even longer.
Compare read times between the c1sus computer, which has its RFM card in the IO chassis, to c1ioo, which has its RFM card in the computer.
No RFM reads: 8 microseconds
3 RFM reads: 20 microseconds (~4 per read)
6 RFM reads: 32 microseconds (~4 per read)
No RFM read: 25 microseconds (bigger model)
1 RFM read: 33 microseconds (~8 per read)
3 RFM read: 45 microseconds (~7 per read)
6 RFM read: Over 62 microseconds, doesn't run.
It looks like moving the RFM card may help by about a factor of 2 in read speed, although its still not quite what Alex and Rolf claim it should be.
The c1mcs and c1ioo models have been reverted to their normal operations.