On Thu, 2011-03-03 at 02:56 +0530, Manu Abraham wrote:
> while in PCIe 1.0 mode it can do 2.5Gbits/s x1 lane
> while in PCIe 2.0 mode it can do 5.0 Gbits/s x1 lane
> PCIe 3.0 mode can do about 8.0 Gbits/s x1 lane

While technically true, there is something here that people often miss
with PCIE.

In PCIE 1.0 and 2.0, the link uses 8/10bit encoding. What this means is
that for every 10 bits sent, 8 bits are data.

So, A PCIE 1.0 x1 physical link operates at 2.5Gbits/s, and that
translates to 250MB/s or data throughput.

Similarly for PCIE2.0 an x1 link operates at 5Gbits/s, and that
translates to 500MB/s.

PCIE3.0 is different. It uses 128/130 encoding. What this means is that
for every 130bits transmitted, 128 of those bits are actual data.

So, although the physical rate is "only" 8Gbits/s, the actual data rate
is indeed 2x PCIE2.0, ~1GB/s.

Not a big deal, but something people often overlook when it comes to
bandwidth. PCIE3 is indeed a 2X jump in transfer rate over PCIE2.0.

TTYL

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