iMac 5K Flash Drive (SSD)

MPG has a 1TB Apple SSD in the Mac Pro, and a 1TB SSD in the iMac 5K.

MPG was puzzled why IntegrityChecker 'verify' was running significantly slower on the iMac, which ought to run significantly faster (faster CPU clock with ~1.4 CPUs used).

Disk I/O speed is the culprit.

Mac Pro: writes at ~930 MB/sec and reads at ~1180 MB/sec.
iMac 5K: writes at ~716 MB/sec and reads at ~766 MB/sec.

The flash drive in the iMac 5K is a two-lane device. With each PCIe lane delivering 500 MB/sec but with ~20% overhead, peak speed is thus limited to ~800MB/sec (theoretical) for the iMac SSD (the Mac Pro allocates 4 lanes).

Real world speeds through the file system using diglloydTools DiskTester.
disktester run-sequential --test-size 8GB

Flash Drive (SSD) Performance
iMac 5K 4 GHz Radeon M295X vs 2013 Mac Pro 3.3 GHz 8-core D700