Intel PRO/1000 PT

[Nikolas Britton]

On 7/3/06, Lowell Gilbert <lowell at be-well.ilk.org> wrote:
> "Nikolas Britton" <nikolas.britton at gmail.com> writes:
>
> > On 7/3/06, Lowell Gilbert <lowell at be-well.ilk.org> wrote:
> >> "Nikolas Britton" <nikolas.britton at gmail.com> writes:
> >>
> >> > What are the difference between the Intel PRO/1000 PT Server and
> >> > Desktop Adapters?
> >> >
> >> > Intel PRO/1000 PT Server Adapter: $130 ~ 150
> >> > Intel PRO/1000 PT Desktop Adapter: $40 ~ 60
> >> >
> >> > Both use the i82572EI chip and both appear to use the same PCB. Would
> >> > I be correct in assuming it's a marketing scam to get 2.5 times the
> >> > price for the same device?
> >>
> >> Look at the specs; they use different controllers (from the same
> >> family, so they may well work in the same PCB, but distinct in
> >> capabilities).
> >
> > To clarify, I'm looking at Intel's PBs (product briefs) here:
> > http://www.intel.com/network/connectivity/products/prodbrf/pro1000_pt_desktop_adapter.pdf
> > http://www.intel.com/network/connectivity/products/prodbrf/pro1000_pt_server_adapter.pdf
> >
> > Look at the first line in the Features list on the first page, Both
> > PBs list the same "Intel 82572EI Gigabit Controller".
>
> Hmm.  Sorry, my notes seem to be wrong (or, given this market, quite
> possibly just out of date).  I thought the "desktop" version was based
> on something else (82751, I would have guessed).
>

The 82571EB is for dual port adapters.

> >> They also have different bus interfaces -- which
> >> could be a sustantial speed advantage for the server version under
> >> high load.
> >>
> >
> > Again the PB clearly states both cards are PCI Express 1x... Just look
> > at the photo in the PB... The cards are identical!
>
> I still think there's a difference there, though; the "server" version
> seems to be 4x.
>

You must be thinking of the Intel PRO/1000 PT Dual Port Server
Adapter... that's a PCIe 4x device.

"Each lane utilizes two low voltage differential (LVDS) signaling
pairs at 2.5 gigabaud. Transmit and receive are separate differential
pairs, for a total of 4 data wires per lane." [1]

"PCIe 1x is often quoted to support a data rate of 250 MB/s (238
MiB/s) in each direction, per lane. This figure is a calculation from
the physical signalling rate (2.5 Gbaud) divided by the encoding
overhead (10bits/byte.) This means a 16 lane (x16) PCIe card would
then be theoretically capable of 250 * 16 = 4 GB/s (3.7 GiB/s) in each
direction." [1]

To summarise, PCIe 1x is 2.5Gbps each way (dual simplex). After you
calculate in overhead (20%) you will have approximately 2Gbps, or
250MB/s, to work with. This is more then enough for a single gigabit
ethernet connection but not enough for two of them, PCIe 4x is 10Gbps
- 20% overhead (8Gbps) each way.

[1] http://en.wikipedia.org/wiki/PCI_Express

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