Testing SATA Express

SATAe is not commercially available yet but ASUS sent us a pre-production unit of the SATA Express version of their Z87 Deluxe motherboard along with the necessary peripherals to test SATAe. This is actually the same motherboard as our 2014 SSD testbed but with added SATAe functionality.

Test Setup
CPU Intel Core i7-4770K at 3.5GHz (Turbo & EIST enabled, C-states disabled)
Motherboard ASUS Z87 Deluxe SATA Express (BIOS 1707)
Chipset Intel Z87
Chipset Drivers
Storage Drivers Intel RST
Memory Corsair Vengeance DDR3-1866 2x8GB (9-10-9-27 2T)
Graphics Intel HD Graphics 4600
Graphics Drivers
Power Supply Corsair RM750
OS Windows 7 Ultimate 64-bit

Before we get into the actual tests, we would like to thank the following companies for helping us with our 2014 SSD testbed.

The ASUS Z87 Deluxe SATA Express has two SATAe ports: one routed from the Platform Controller Hub (PCH) and the other provided by an ASMedia ASM106SE chip. The ASMedia is an unreleased chip, hence there is no information to be found about it and ASUS is very tight-lipped about the whole thing. I'm guessing we are dealing with the same SATA 6Gbps design as other ASM106x chips but with added PCIe pass-through functionality to make the chip suitable for SATA Express.

I did a quick block diagram that shows the storage side of the ASUS SATAe board we have. Basically there are four lanes in total dedicated to SATAe with support for up to two SATAe drives in addition to four SATA 6Gbps devices. Alternatively you can have up to eight SATA 6Gbps devices if neither of the SATAe ports is operating in PCIe mode.

Since there are no SATAe drives available at this point, ASUS sent us a SATAe demo daughterboard along with the motherboard. The daughterboard itself is very simple: it has the same SATAe connector as found in the motherboard, two molex power inputs, a clock cable header, and a PCIe slot.

This is what the setup looks like in action (though as you can see, I took the motherboard out of the case since inside case photos didn't turn out so well with the poor camera I have). The black and red cable is the external clock cable, which is only temporary and won't be needed with a final SATAe board.

The Tests

For testing I used Plextor's 256GB M6e PCIe SSD, which is a PCIe 2.0 x2 SSD with Marvell's new 88SS9183 PCIe controller. Plextor rates the M6e at up to 770MB/s read and 580MB/s write, so we should be capable of reaching the full potential of PCIe 2.0 x2. Additionally I tested the SATA 6Gbps ports with a 256GB OCZ Vertex 450. I used the same sequential 128KB Iometer tests that we use in our SSD reviews but I ramped up the queue depth to 32 to make sure we are looking at a maximum throughput situation.

Iometer—128KB Sequential Read (QD32)

There is no practical difference between a PCIe slot on the motherboard and PCIe that is routed through SATA Express. I'm a little surprised that there is absolutely no hit in performance (other than a negligible 1.5MB/s that's basically within the margin of error) because after all we are using cabling that should add latency. It seems that SATA-IO has been able to make the cabling efficient enough to transmit PCIe without additional overhead.

As for SATA 6Gbps, the performance is the same as well, which isn't surprising since only the connector is slightly different while electrically everything is the same. With the ASMedia chipset there is ~25-27% reduction in performance but that is inline with the previous ASMedia SATA 6Gbps chipsets I've seen. As I mentioned earlier, I doubt that the ASM106SE brings anything new to the SATA side of the controller and that's why I wasn't expecting more than 400MB/s. Generally you'll only get full SATA bandwidth from an Intel chipset or a higher-end SATA/RAID card.

Iometer—128KB Sequential Write (QD32)

The same goes for write performance. The only case where you are going to see a difference is if you connect to the ASMedia SATA 6Gbps port. I did run some additional benchmarks (like our performance consistency test) to see if a different workload would yield different results but all my tests showed that SATAe in PCIe mode is as fast as a real PCIe slot, so I'm not going to post a bunch additional graphs showing that the two are equivalent.

NVMe vs AHCI: Another Win for PCIe Final Thoughts
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  • SirKnobsworth - Thursday, March 13, 2014 - link

    We have both eSATA and SATAe now. This is going to be fun...
  • sheh - Thursday, March 13, 2014 - link

    Sadly eSATA isn't that common.
  • kwrzesien - Wednesday, April 30, 2014 - link

    SATAe won't be either.
  • fokka - Thursday, March 13, 2014 - link

    this is cable design straight from hell. an ide connector is more attractive than this.
  • tspacie - Thursday, March 13, 2014 - link

    Oh, please let there be a full review of that Plextor M6e in the near future. I have a computer with no 6Gbps SATA ports, but plenty of PCIe slots just desperate for faster storage.
  • Gc - Thursday, March 13, 2014 - link

    TheSSDReview has looked at a Plextor M6e a couple times now with different host cards.
  • Kristian Vättö - Friday, March 14, 2014 - link

    It's coming ASAP. I've had the drive for ~2 months now but unfortunately there have been issues with testing (it's the first PCIe drive I'm testing). The drive runs in PCIe 1.0 (i.e. ~350MB/s max) if it's connected to a PCIe 2.0 slot and my motherboard doesn't offer the option to force certain PCIe mode, so I've been waiting for a firmware update to fix this. Similarly, some of our benchmarks don't like the combination of PCIe SSDs and our new testbed and we are still in the process of figuring those issues out. As soon as I'm sure the drive is operating as it should, I'll start working on the review :)
  • tspacie - Friday, March 14, 2014 - link

    Thanks for doing all the leg work!
  • bj_murphy - Thursday, March 13, 2014 - link

    Could you clarify what you mean by "half height/length PCIe" when you are speaking about the 4 major form factors of flash storage on the final page? Isn't that the exact same connector as mSATA or am I thinking of something else?
  • sheh - Thursday, March 13, 2014 - link

    Same connector as mPCIe, different signals.

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