I have a MV-III with a DEQNA interface and RQDX3
w/RD54,
and a MOP boot with all filesystems *and* swap on remote NFS
partitions is considerably faster than running on the RD54.
My impression is that in order of performance it goes MFM -> DSSI
-> SDI and that the vS3500 was considered a performance machine,
leading to the 3520 and '40. (going out on a limb now) I would actually
be surprised if DEC ever shipped a vS3500 with MFM drives.
Perhaps TMaC's system was customised by a prior user?
John A.