OWC Mercury Accelsior 480GB PCIe SSD Review – First Upgradeable PCIe SSD Hits The Streets

It was only a matter of time before the idea of expandable storage was introduced into the world of PCIe SSDs and, although we have seen a few prototypes in the last year, none have quite made it to market just yet.

Our analysis of the OWC Mercury Accelsior 480GB PCIe SSD not only opens the possibility of upgradeable capacity sizes, but also, it just so happens to be only the second consumer targeted PCIe SSD on the market right now and is both Mac and PC ‘plug and play’ compatible.


The OWC Mercury Accelsior is available in capacities of 120, 240 480 and 960GB.  There are three detachable components which are the PCIe itself and two upgradable ‘blade’ mPCIe SSDs that can be switched off for higher capacity.  Performance of the Accelsior does not suffer the SATA 3 bottleneck at 600MB/s and speeds are listed at 780MB/s read and 648MB/s write.

Similar to only the SuperTalent RAID Drive upStream prototype that we reviewed, the Mercury Accelsior requires no driver installation and is plug and play. Simply insert it into an available PCIe slot in your system and reboot. The Mercury Accelsior has a three year warranty, is available now, and prices are $359.99 (120GB), $529.99 (240GB), $949.99 (480GB) and $2079.99 (960GB). In a search, we found the Accelsior available at OWC and Amazon.Com, for those who want the bigger capacity and can use AmazonPayments.


The OWC  Mercury Accelsior contains a PCIe card and two detachable ”blades’ which are mPCIe SSDs that are typically spoken of as being a ‘gumstick’ design because of their look, although OWC prefers to call them ‘blade’ drives.  The performance of the Accelsior is a result of running both SSDs in a RAID 0 configuration which increases their performance significantly.

blankThe main card houses a Marvell 88SE9230 RAID controller under the heatsink which is significantly small in size and prevents removal of the heatsink for shots.  This host controller connects the two SATA 3 SSDs to the PCIe 2.0 host and will allow up to 1GB/s bandwidth in ideal conditions.  The controller actually supports four devices which becomes an interesting consideration when you look at the back of the card.

blankEach mPCIe blade SSD contains the SandForce SF-2281 controller and eight pieces of Toshiba 32Gb 24nm Toggle Mode mlc NAND flash memory for a total of 256GB RAW capacity on each SSD.  SandForce firmware and over provisioning needs reduce the capacity of each to 240GB which provides for 480 total advertised capacity.

blankblankFinal formatted capacity is 447 GB, but remember, this is one of those rare storage devices where you can upgrade the capacity as needed and as it becomes affordable. Here is a pik of the card in one of our Test Bench’s:



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    Is it bootable?

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    can i use trim comand? does it have a garbage collector? after intensive use of the drive will it perform slower?

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      No TRIM would not work with this RAID 0 configuration, however, Garbage Collection would do its job with the SandForce drives. Unfortunately, the product doesn’t remain with us for a long period so any degradation cannot be measured through continuance use and analysis.

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      no, yes, yes

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    Does the drive maintain the same performance figures in its smaller configuration (120GB)?

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    It seems wrong to call this card a PCIe SSD card as such since it is really a Raid/HBA card which happens to accept mPCIe SSD’s on the board itself. And just why wasn’t this card manufactured with the ability to install 4 mPCIe SSD’s from the get go?

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      The Accelsior uses the Marvell 88SE9230 which only supports PCIe 2.0 x2 which only allows up 1000 MB/s. You would need to use a chip with 4 lanes (such as the Marvell 88SE9445) to get the full performance out of 4 SSD’s. Maybe that chip doesn’t have the boot ability that OWC advertises.

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    Would you happen to know/offer any card or adaptor to connect an SSD like this (https://www.toshiba.com/taec/news/press_releases/2010/memy_10_604.jsp) and retrieve the data? It is the SSD from an Asus UX31 and I think the connection is similar to the ones of the SSDs in the newer versions of the Macbook Air.

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    Please run CrystalDewWorld’s DiskMark with a larger test size. At 1000MB, the filesystem cache can skew results upwards. For example, running DiskMark w/1000MB on my system shows read/write operations around 480MB/s. Cranking up the test size to 4000MB returns a more realistic 290MB/s — appropriate for a SATA II SSD drive.

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    I’m a bit puzzled as to exactly a PCIe SSD card does for a computer. I have an older Intel MAC Pro tower used mostly for audio recording and am trying to extract a bit more performance from the box during in-the-box multi-track audio recording. Does this device essentially only increase the read/write performance between the computer and external drives or are there other benefits? TIA

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    spotted something that needs correction in your review- SandForce SF-2281 is a SATA controller not PCIe, and the Marvell RAID controller is also a SATA part. Not sure where you got the idea that the SSDs in this review were PCIe, but they are not.

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      The review is correct and it is not stated that the SF-2281 is a PCIE controller. This package is a PCIE product, in that, it is connect d via this route. Thanks anyway.

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        Thanks for your quick reply- however your review states
        ‘There are three detachable components which are the PCIe itself and two upgradable ‘blade’ mPCIe SSDs that can be switched off for higher capacity.’
        You have clearly referred to the SSDs as mPCIe which is not correct. Thanks anyway.

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        I am curious what validation you might have to prove this. Considering both the RAID controller and SSD controller are both PCIE compliant, your opinion should be validated in some way. Simply because the connector of the blade SSDs is custom, does not mean the term still cannot be used for best explanation to the reader, similar to the way one compares an Apple SSD to that of the M2.

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        The use of mPCIe was used as the best explanation at the time for the custom connector. While you are correct that the controller is SATA on each blade SSD, this custom solution is a PCIE design. Thanks again.

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