Ethernet Card

[el_pedriyo]

Hello guys,

I was thinking about purchasing a 4 ethernet pors PCIe card, and found some of these:

Amazon CAPTCHA

The only thing I was thinking about is, why is that card a pcie x4 and not just simply a pcie x1? As looking around pcie2.0 x1 is 4 Gbit/s

Any idea you might think?

Kind regards

 

[reasonsandreasons]

I am not an expert on this so other folks should feel free to chime in, but my impression is that gigabit Ethernet is full duplex, so it's capable of both sending and receiving at gigabit speeds simultaneously. So if your numbers are correct there you'd want at least a PCIe2 x2 link to handle that bandwidth, plus some overhead to be on the safe side. Physical x2 cards aren't really made, so they round up to x4.

(A side note: I'm not sure how the used market is where you are but in the US used quad-port gigabit NICs are pretty cheap, so that might be an option worth checking out.)

 

[LVLouisCyphre]

Simple, x1 can't handle it. I had a server farm of EISA/PCI FreeBSD servers; one with a 3C597TX card. In 100BTX mode it ran only at half duplex. Why? Because the EISA bus can't handle 100BTX full duplex.

Your card should work with the em(4) driver. I have an Intel Pro/1000 PT quad port on the way for under $20 (USD), it's also a x4 and uses the same driver. When you go to multiport GbE, you are looking at x4 cards especially with backward compatibility with PCIe 1.x. When quad port 1 GbE cards hit the market they were designed for PCIe 1.x. When a PCIe card manufacturer designs a card, they have to make it backwards compatible with PCI 1.x which is slower than PCIe 2.x. With every version of PCIe, they basically bump the speed limit of the lanes; same evolutionary technology principle as with networking (10BASE on up to 50GBASE and the WiFi 802.11 alphabet soup) and storage devices (SCSI, PATA, SAS and SATA).

I am not an expert on this so other folks should feel free to chime in, but my impression is that gigabit Ethernet is full duplex, so it's capable of both sending and receiving at gigabit speeds simultaneously. So if your numbers are correct there you'd want at least a PCIe2 x2 link to handle that bandwidth, plus some overhead to be on the safe side. Physical x2 cards aren't really made, so they round up to x4.

(A side note: I'm not sure how the used market is where you are but in the US used quad-port gigabit NICs are pretty cheap, so that might be an option worth checking out.)

You are correct, sir!

You can run 1 GbE at half duplex in rare instances; Cisco Gigastack GBICs with what looked like firewire ports did that if you used both links in a daisy chain.