So I dug in and learned some new things, so I figured I'd share what I "found out" about my "problem"...
as I've been spending a lot of time researching this issue, I headed on
over to Wikipedia. There, I found an article on PCI-e 2.0, which
clearly states that it has maximum per-lane transfer rate of 500MB/s,
rather than what I originally thought - 250MB/s. Apparently, 250MB/s
was actually the limit for legacy PCI-e 1.x connections. This means
that any single-lane PCI-e x1 card (providing it is a PCI-e 2.0 device)
should allow me to run up to 500MB/s of data throughput, as long as I
connect it to a PCI-e 2.0 slot. And 500MB/s should certainly be enough
to support my SSD's 355MB/s max read performance... >In
fact, I now know that I absolutely cannot use the Asus US36 as originally hoped; however, I also found the StarTech PEXSAT32 PCI-e x1 SATA
6Gbps add-in card. On this card's tech specs page, there's a notation
at the very bottom of the page which confirms my calculations above. It
states that PCI-e 1.x slots would limit the card to 2.5Gbps (250MB/s),
whereas the same card in a PCI-e 2.0 slot would allow it to run at the
full PCI-e 2.0 maximum lane rate of 5Gbps (500MB/s). Now granted, 5Gbps
still does not the full possible throughput of SATA III (6Gbps) - as
that would only be possible on a 4x, 8x, or 16x PCI-e card, where your
total possible bandwidth is multiplied further. In this case, even
just a PCI-e x4 card would support up to 2GB/s of data transfer, which
is well over the 600MB/s possible in the new ATA III standard.
Regardless though, my Crucial C300 caps out at 355MB/s so the StarTech
PCI-e x1 card's 5Gbps (e.g. 500MB/s) bandwidth limitation doesn't impact
me much, if at all.
>In case any of you are interested, - for
your reference, here are the links I used to do the solve my SSD SATA
6Gbps throughput mystery:
>PEXSAT32 Technical Specifications:>http://www.startech.com/item-specs/PEXSAT32-2-Port-SATA-6-Gbps-PCI-Express-SATA-Controller-Card.aspx>
PCI-Express 2.0 Wiki:>http://en.wikipedia.org/wiki/PCI_Express#PCI_Express_2.0
I hope this helps someone, like it helped me!
All the best!