Crucial’s RealSSD C300 - The Perfect Test Candidate

The C300 is capable of pushing over 300MB/s in sequential reads. More than enough bandwidth to need 6Gbps SATA as well as expose limitations from PCIe 1.0 slots.

To test the C300 I’m using Highpoint’s RocketRAID 62X. This PCIe 2.0 x1 card has a Marvell 88SE9128 6Gbps controller on it.

What About P5x/H5x?

Unlike Intel’s X58, the P55 and H5x chipsets don’t have any PCIe 2.0 lanes. The LGA-1156 Core i7/5/3 processors have an on-die PCIe 2.0 controller with 16 lanes, but the actual chipset only has 8 PCIe 1.0 lanes. And as we’ve already established, a single PCIe 1.0 lane isn’t enough to feed a bandwidth hungry SSD on a 6Gbps SATA controller.

Gigabyte does the obvious thing and uses the PCIe 2.0 lanes coming off the CPU for USB 3 and 6Gbps SATA. This works perfectly if you are using integrated graphics. If you’re using discrete graphics, you have the option of giving it 8 lanes and have the remaining lanes used by USB 3/SATA 6Gbps. Most graphics cards are just fine running in x8 mode so it’s not too big of a loss. If you have two graphics cards installed however, Gigabyte’s P55 boards will switch to using the PCIe 1.0 lanes from the P55/H5x.

ASUS uses the same approach on its lower end P55 boards, but takes a different approach on its SLI/CF P55 boards. Enter the PLX PEX8608:

The PLX PEX8608 combines 4 PCIe x1 lanes and devotes their bandwidth to the Marvell 6Gbps controller. You lose some usable PCIe lanes from the PCH, but you get PCIe 2.0-like performance from the Marvell controller.

For most users, ASUS and Gigabyte’s varying approaches should deliver the same results. If you are running a multi-GPU setup), then ASUS’ approach makes more sense if you are planning on using a 6Gbps SATA drive. The downside is added cost and power consumed by the PLX chip (an extra ~1.5W).

The Primer: PCI Express 1.0 vs. 2.0 The Test Platforms
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  • Shadowmaster625 - Tuesday, March 30, 2010 - link

    It sounds like AMD made a conscious decision to focus on maximum random write performance, even if it required sacrificing all other key performance metrics. I hope that is the case, because it is pretty sad that their 6 gbps controller is generally outperformed by a 3 gbps controller!
  • astewart999 - Tuesday, March 30, 2010 - link

    When talking performance, why are they not mentioning RAID 0. I suspect SATA3 is not capable?
  • astewart999 - Tuesday, March 30, 2010 - link

    Ignore my ignorance, I read the article then posted. Should have read the posts and ignored the article!
  • nexox - Monday, April 5, 2010 - link

    Just get a SASII (6Gbit) PCI-E HBA (LSI makes one, probably others) - plenty of speed, they generally run on a PCI-E 8x slot, and you can run SATA drives in them just fine. Plus they tend not to cost too much more than the consumer-level SATA adaptors, which are apparently questionable performance-wise. They'd at least make a good baseline for comparison.
  • supremelaw - Saturday, April 17, 2010 - link

    RS2BL040 and RS2BL080 are now at Newegg:

    Before buying, confirm whether or not TRIM will work with SSDs in RAID modes.

    *** UPDATE ***

    The unconfirmed bit has been confirmed as unconfirmed from Intel:

    “Intel® RST 9.6 supports TRIM in AHCI and pass through modes for RAID. A bug has been submitted to change the string that indicates TRIM is supported on RAID volumes (0,1,5,10). Intel is continuing to investigate the ability of providing TRIM support for all RAID volumes in a future release”

    Looks like we'll have to wait a little longer for TRIM through RAID, but there *are* other SSD-specific improvements in this new driver.

    *** END UPDATE ***

  • chrcoluk - Saturday, June 19, 2010 - link

    Ok my thoughts.

    1 - you written of pcie v1 however failed to notice or mention that the plx chip uses pci-e 1x lanes from the p55 chipset so clearly pci-e 1.0 can supply the bandwidth if utilised properly, the plx chip transfers 4 1.0 lanes into 2 virtual 2.0 lanes for the sata6g and usb3.
    2 - some p55 boards, mine noticebly have a pci 2.0 slot fed of the p55 chipset @ x4 speed. Seems reviewers have got something wrong or are they claiming asus have it wrong? Even if we assume its actually pci 1.0 x4 that is still enough bandwidth to feed a sata 6g controller. Indeed the onboard plx which you praised sacrifices this x4 pci-e slot and uses those 4 lanes to feed itself. My thoery is the U3S6 card asus sell will perform the same as the onboard plx in a x4 slot but no reviewer has tested this properly.
    3 - whats the reason you did not test both gigabytes onboard and the lower asus onboard which borrow bandwidth from the primary pci-e x16 lanes, I am looking for tests of those in both turbo/levelup and normal mode.
  • gimespace - Tuesday, August 8, 2017 - link

    Try enabling DirectGMA with maximum GPU Aperture in Amd catalyst control center. It does not only make the graphics card faster but allowed me to get up to the maximum 560mb/s read speed for my ssd!

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