Motherboard bottlenecking NIC?

[Masonrk]

Hello TH,

I am planning in building a pfsense router out of an old dell IDE desktop(just to be safe lets say its a 2002). What I am worried about is that my network is all gigabit. And I want to make sure that this old desktop PCI bus can take gigabit speeds without bottlenecking.

Any thoughts guys and gals?

 

[Darkbreeze]

Here's a thread on that exact question and the general consensus is that it's most likely not able to keep up. Plus, the remainder of the system, aside from the PCI bus for the network card may not be sufficient either.

Short answer: Probably not
Long answer: The PCI bus can sustain 133 MBytes/sec for the normal case. A PCIe x1 slot can sustain 250MBytes/sec. 1Gbit/sec = 125MBytes/sec. So if the question is purely as to whether a PCI bus can take all that data, the answer is yes. Now, you do have to add overheads to that, but they're relatively minor. That said, the PCI bus is shared; This means that if you have other PCI devices, the bandwidth available to the network card may not in fact be 125 MBytes/sec.

However, you're unlikely to ever attain 1Gbit/sec. The reason is as follows:

If you use the largest MTU available to you that is compatible with 100 MBit equipment (1500 bytes), that comes out at 83333 packets/second. Put simply, if you're using Windows, you're far more likely to notice SMB RPC overheads associated with your file copying (if you're copying it by the normal means) than anything else. Furthermore, if the driver used is using DMA interrupts instead of polling (which is normal on Windows as I understand it), you're likely to peg the CPU in so doing.

http://forums.whirlpool.net.au/archive/1270738