Rookie_MIB :
Unfortunately with those CAS timings they're really no better than 2133 CAS 9 DDR3..
4266/CAS19 = 217
2133/CAS9 = 237 which means more operations/second
It is still improvement though. The bandwidth is much greater 68,256 MB/s vs 34,128 MB/s. The access time is a little slower than than a DDR3 2133/CAS9 kit, 8.9ns for the 4266 MHz kit vs 8.4ns for the DDR3, but you are transferring twice the amount of data each time. The end result is that the DDR3 kit mentioned here would achieve 18 cycles in the time it takes the DDR4 kit here to complete 17 cycles. The DDR4 is still better, however, because in 17 cycles it will provide 1,160,352 MB/s of bandwidth, while the DDR3 only provides 614,304.