[plug] gigabit lan

Adrian Chadd adrian at creative.net.au
Wed Jan 9 19:25:19 WST 2008

On Wed, Jan 09, 2008, Brad Campbell wrote:

> (all measurements in Mega BITS)
> I was hoping for more, but given all the athlons are VIA chipsets with the 
> NIC's sitting on the PCI bus, and the hardware is now 4 years old I guess I 
> can't complain that much. Disappointed with the performance of the Mac Mini 
> though.

the mac mini gige ports shouldn't be on a slow PCI bus internally, but
then I don't own one.

The trouble is this. If you've got a gige chipset on a junk PCI 32 bit/33mhz
bus then your max transfer rate won't ever hit 1gig. With my testing I've
reached ~350mbit full duplex (so 350mbit in and out) using 1518 byte frames
(ie, not jumbo frames.)

But then I did all the right stuff - disabled delayed ack/sack, wound my
send/receive buffers right the heck up, tuned the polling parameters, etc.
The defaults aren't always great for gige LAN networking.

Of course, if you have a junk board that has all the PCI slots and the NIC
on the same 32-bit 33mhz PCI bus and you're doing lots of disk IO then
you're halving (at least) the throughput - as the same bus needs to shuffle
disk IO and then shuffle it back out the network port.

Thats why I love PCIe. No shared busses, right? :)


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