Congrats ,
your contribution to "" has been selected as the Best Answer.
Click here to review this thread: http://www.tomshardware.co.uk/forum//forum2.php?config=tomshardwareuk.inc&cat=30&post=265688&page=1&p=1
Thank you for contributing the Tom's Hardware community
The Tom's Hardware community team

New URL:

http://www.tomshardware.com/forum/265688-30-bottleneck-pciexpress

Best solution

MRFS

November 11, 2009 3:44:28 PM

We're monitoring the transition to SATA/6G storage devices,
and the best explanation we have been able to find to date
came in a block diagram prepared by the good folks at
PC Perspective, founded by Ryan Shrout.

Here's that block diagram:



And, here's the source article:

http://www.pcper.com/article.php?aid=769


Ryan & company were one of the first to illustrate this implementation:
it does NOT provide the maximum bandwidth of the SATA/6G standard
i.e. 6 Gbps / 10 bits per byte (serial protocol) = 600 MB/sec.


Summary, "PCIe x1 Gen2" means x1 PCI-Express lane @ 250 MB/second x 2 (Second Generation)
= 500 MB/second bandwidth ceiling, one direction.


If you want true "6G" bandwidth, check out Intel's RS2BL040 and RS2BL080 controllers:

http://www.intel.com/Products/Server/RAID-controllers/R...
http://www.intel.com/Products/Server/RAID-controllers/R...

LSI SAS2108 ROC technology, x8 PCI Express Generation 2 host interface and 800 MHz cache enhances the performance of mainstream applications.


Also, I think the ASUS U3S6 add-in card has the same 500 MB/sec. limitation,
because it uses the same chips as found on their P7P55D Premium motherboard:

http://www.newegg.com/Product/Product.aspx?Item=N82E168...


We've asked our Channel supplier to order a U3S6 card for us,
but he recently told us it's not yet available. Lots of photos
of the U3S6 are here:

http://www.maximumpc.com/article/news/exclusive_first_u...


I hope this helps.


MRFS