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


New-System-CloseUp This is The SSD Review Test Bench Number One. A quick click on the photo will give you a better look.

In testing, our main objective is to obtain results as pure and as accurate as possible and we want to ensure that no anomalies slip through. Simply put, we want to provide you with the absolute best results the tested hardware can provide. Repetition in testing is standard and, if necessary, we may conduct specific tests in Windows 7 ‘safe mode’ to ensure the OS has little to no influence on the end result.

In order to validate and confirm our findings, testing is supported by industry accepted benchmark programs. All results are displayed through capture of the actual benchmark for better understanding of the testing process by the reader.


We would like to thank Gigabyte, Corsair, MSI, OCZ, and Fractal-Design, for sponsoring components of our Test Bench.


All SSDs are not created equal and many new SSD enthusiasts realize that when they test their new drive to confirm specifications and ensure all is in order. LSI SandForce controlled SSDs, as in the OWC Mercury Accelsior 480GB PCIe we are testing today, use compression techniques in storage whereas many others do not. This creates a bit of confusion when enthusiasts test the drive with random data through benchmarking programs such as AS SSD and Crystal Diskmark. The results seem to be lower than the listed specifications.


Under normal circumstances one might observe a difference between the Accelsior and another ‘non-SandForce’ controlled PCIe card, however, the only other on the market is also ‘SandForce Driven. This then brings us to the Marvell 88SE9230 6Gbps controller which might also have an impact on testing and is one that we are not familiar with which makes things all that much more interesting.


The software we will be using for today’s analysis is typical of many of our reviews and consist of ATTO Disk Benchmark, Crystal DiskMark, AS SSD, Anvil Storage Utilities, HDTune Pro and PCMark Vantage.  We rely on these as they each have a way of supporting one another yet, at the same time, adding a new performance benchmark to the total picture.  Much of the software is free and can be downloaded simply by clicking on the linked title.


ATTO Disk Benchmark is perhaps one of the oldest benchmarks going and is definitely the main staple for manufacturer performance specifications. ATTO uses RAW or compressible data and, for our benchmarks, we use a set length of 256mb and test both the read and write performance of various transfer sizes ranging from 0.5 to 8192kb. Manufacturers prefer this method of testing as it deals with raw (compressible) data rather than random (includes incompressible data) which, although more realistic, results in lower performance results.

blankInitial specifications listed 780MB/s read and 648MB/s write whereas our ATTO result shows highs of 765MB/s read and 740MB/s write, write performance being just short of 100MB/s higher than listed specifications.


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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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