Date: Mon, 3 Jul 2006 12:34:32 -0500 From: "Nikolas Britton" <nikolas.britton@gmail.com> To: "Lowell Gilbert" <lowell@be-well.ilk.org> Cc: freebsd-questions@freebsd.org Subject: Re: Intel PRO/1000 PT Message-ID: <ef10de9a0607031034oab509c5t811e00164ce626c4@mail.gmail.com> In-Reply-To: <44wtau64h9.fsf@be-well.ilk.org> References: <1151753054.00556526.1151742601@10.7.7.3> <44y7valtc0.fsf@be-well.ilk.org> <ef10de9a0607030841y74c60b5bq7d543a3ec4d08199@mail.gmail.com> <44wtau64h9.fsf@be-well.ilk.org>
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On 7/3/06, Lowell Gilbert <lowell@be-well.ilk.org> wrote: > "Nikolas Britton" <nikolas.britton@gmail.com> writes: > > > On 7/3/06, Lowell Gilbert <lowell@be-well.ilk.org> wrote: > >> "Nikolas Britton" <nikolas.britton@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 possibly just out of date).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 -- BSD Podcasts @: http://bsdtalk.blogspot.com/ http://freebsdforall.blogspot.com/
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