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Mac Pro Tower Upgrade:
Amfeltec Squid PCIe 3.0 Carrier Board for M.2 flash blades

Originally posted November 29th, 2016 by rob-ART morgan, mad scientist

A year ago we shocked you with achieving close to 6000MB/s large sequential transfer speeds with a 2010 Mac Pro sporting the Amfeltec PCIe 2.0 M.2 carrier board with four M.2 SM951 AHCI blades in a RAID 0 set. In this article, we chronicle our experience with PCIe 3.0 Carrier Board with the same four M.2 SM951 AHCI blades. You will be shocked, but not in the way you think.

Gen2 Quad 4*flash = Amfeltec Squid PCIe 2.0 x16 Carrier board for M.2 SSD modules with four 512G Samsung SM951 AHCI flash blades
Gen2 Quad 3*flash = Amfeltec Squid PCIe 2.0 x16 Carrier board for M.2 SSD modules with three 512G Samsung SM951 AHCI flash blades
Gen3 Quad 4*flash = Amfeltec Squid PCIe 3.0 x16 Carrier board for M.2 SSD modules with four 512G Samsung SM951 AHCI flash blades
Gen3 Quad 3*flash = Amfeltec Squid PCIe 3.0 x16 Carrier board for M.2 SSD modules with three 512G Samsung SM951 AHCI flash blades
Gen3 Quad 2*flash = Amfeltec Squid PCIe 3.0 x16 Carrier board for M.2 SSD modules with two 512G Samsung SM951 AHCI flash blades
Gen3 Quad 1*flash = Amfeltec Squid PCIe 3.0 x16 Carrier board for M.2 SSD modules with one 512G Samsung SM951 AHCI flash blade

In the first two graphs, the Amfeltec Squid PCIe Quad-Slot M.2 Carrier Board was installed in the x16 PCIe 2.0 slot 2 of a 2010 Mac Pro 6-core 3.33GHz. In the second pair of graphs, it was installed in the x16 PCIe 3.0 slot of a Hackintosh (Gigabyte GA-Z97X-UD3H motherboard).


We used AJA System Test to benchmark file level sequential transfer speed using a 16GB test file (and 4K frame size).
LONGEST graph bar means the fastest overall in Megabytes per Second.

What? Why is the PCIe 3.0 version stuck at 3000MB/s?
It is likely that, because the Mac Pro tower's slots are PCIe 2.0 rated, the PCIe 3.0 Carrier Board's controller gets 'lost in translation.' However, when we tried the PCIe 3.0 Carrier Board in a Hackintosh with an x16 PCIe 3.0, the transfer rate with 3 or more flash blades was much higher (see next two graphs).


That's more like it.
The transfer speeds attained on the Hackintosh confirm that the PCIe 3.0 Quad-Slot Carrier Board is 'happier' in an x16 PCIe 3.0 slot. Even higher transfer speeds are likely if and when we find a test platform that supports striping of NVMe flash blades like the Samsung 950 Pro and 960 Pro. (The same goes for the dual-slot version.)

If you have a 2009 - 2012 Mac Pro tower (x16 PCIe 2.0), you will get best performance with the Amfeltec PCIe 2.0 quad-slot M.2 carrier board. If you have a Windows PC or Hackintosh with x16 PCIe 3.0 slots, the Amfeltec PCIe 3.0 quad-slot M.2 carrier board is the way to fly. The same is true of the Amfeltec PCIe 3.0 dual slot M.2 carrier board which maxes out at 1500MB/s in the Mac Pro tower and 3000MB/s in the Windows PC or Hackintosh.

But does the Amfeltec board boot OS X? Yes. However, the OS X installer warns that the resulting volume will not support FileVault or Recovery Partition.

What about heat? With the PCIe 2.0 Carrier Board the SM951 AHCI blades reported temps of 158F, 160F, 158F, and 165F under sustained stress. Those are right at or just above the recommended maximum of 158F by Samsung. It would be worse but for an air gap above and below the mounted flash blades. However, we added some low profile aluminum heatsinks to the SM951 AHCI blades to get the temperatures even lower.

Though the PCie 3.0 Carrier Board produced a maximum transfer speed in the Mac Pro tower of 3000MB/s, it has the added advantage of a fan on the back edge. Therefore the SM951 AHCI blades ran much cooler than the PCIe 2.0 Carrier Board -- even without a heatsink. However, the fan runs constantly and is noticeable -- especially with the side cover removed from the Mac Pro. BTW, Amfeltec now includes their own low profile heatsinks in the kit.

NVMe versus AHCI flash? You may have noticed that we specified "SM951 AHCI" throughout this article. That is to bring to your attention that OS X does not support external, third party NVMe flash blades. However, a driver is available from MacVidCards that provides support for NVMe blades on all models of Mac running OS X El Capitan or earlier. The NVMe driver is NOT compatible with macOS Sierra at this time. Also you will only be able to use the NVMe blades for storage of data. The need to load the third party driver prohibits booting Mac OS X from an NVMe volume.

(We also encountered errors and hangs when we attempted to stripe the NVMe 950 Pros with SoftRAID. Not sure what that is about unless it is a limitation of the NVMe driver.)

The speed advantage of NVMe flash is nullified on the Mac Pro tower.
When it comes to the Mac Pro tower, the NVMe blades won't run any faster than AHCI blades since the PCIe 2.0 x4 slots (3 and 4) top out at 1500MB/s. Even in the case of the Squid card in the PCIe 2.0 x16 slot 2, each individual blade is 'assigned' only x4 bandwidth, thereby limiting it to 1500MB/s. Higher speeds with multiple striped SM951 AHCI blades is accomplished through multiplication via a PCIe switch.

"But AHCI versions of SM951s have become scarce and expensive!"
Yes. True and frustrating. We were able to add a few more AHCI SM951s to our inventory by searching eBay. However most sellers have doubled and tripled the 512G price to profit from the scarcity. If that changes or I find an affordable source, I'll post it on my Twitter account.

Check out the speeds we got with two striped SM951s when an Amfeltec board was placed in a Thunderbolt 3 PCIe Box and connected to the 2016 MacBook Pro!

Feedback or comments? Feel free to email me,
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copyright 2015 Rob Art Morgan
"BARE facts on Macintosh speed FEATS"