The 'late 2015' iMac 5K Flash: How Much Faster Than Before?
Posted October 22nd, 2015 by rob-ART morgan, mad scientist
October 27th, 2015, added Fusion drive
Apple touted the 'late 2015' 27" iMac 5K as having flash storage speed "up to 2.5 times faster than the previous version." Is it true?
GRAPH LEGEND
iMac 5K '15 Flash = 'late 2015' iMac Retina 5K 4.0GHz Quad-Core i7; Radeon R9 M395X GPU; 16G RAM; 1TB flash storage
iMac 5K '15 Fusion = 'late 2015' iMac Retina 5K 4.0GHz Quad-Core i7; Radeon R9 M395X GPU; 16G RAM; 2TB Fusion drive
iMac 5K '14 Flash = 'late 2014' iMac Retina 5K 4.0GHz Quad-Core i7; Radeon R9 M295X GPU; 16G RAM; 1TB flash storage
nMP 4c Flash = 'late 2013' Mac Pro 3.7GHz Quad-Core Xeon; 16G RAM; dual FirePro D300 GPUs; 512G flash storage
AJA SYSTEM LARGE SEQUENTIAL DATA TRANSFER
It uses file level i/o to simulate large sequential video capture and playback. We used 16GB Test Size and 4K frame size. (RED graph bar means FASTEST in Megabytes per Second.)
QUICKBENCH SMALL RANDOM DATA TRANSFER
This is a test of small random transfers ranging from 4K to 1024K bytes. (RED graph bar means FASTEST in Megabytes per Second.)
CONCLUSION
The 'late 2015' iMac 5K's 1TB flash storage speed has definitely taken a leap forward. Part of the improvement has come from increased Link Width (from x2 to x4) and better Link Speed (from 5GT/s to 8GT/s). I assume the Apple proprietary version of the Samsung SM951 flash blade is also present.
On October 27th, we added the 2TB Fusion drive to the graphs. Note that the large sequential READ speed is close to the pure Flash drive but the WRITE speed of the Fusion is less than half that of the Flash. We confirmed that the 2TB and 3TB Fusion have 128G of Flash fused to the HDD but in previous tests, we saw both read and write speed drop precipitously when the Flash module overflowed onto the HDD.
Finally we included the results for the 'late 2013' Mac Pro's XP941 based flash. BTW, if you can find a donor SM951 based flash blade from a recent MacBook Pro or iMac to install in your Mac Pro, its large sequential transfer speed will jump from 1000MB/s to 1500MB/s.
Don't miss these other 'late 2015' iMac 5K test pages:
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