21143 specific problems

David Sean Friedman dsf+@andrew.cmu.edu
Thu Sep 30 00:31:08 1999

Excerpts from tulip: 29-Sep-99 Re: 21143 specific problems by Metod
> I've had similar problems regarding performance of 21143-based NIC in FD
> mode. I solved it by using the NIC in HD mode.
You're right. By forcing the NIC into half duplex mode, performance went
up to ~80Mb/s. I was also surprised to see TCP receive performance
improve from ~60 to ~80Mb/s in half duplex mode. 

Using half duplex should clearly not have better performance for TCP

> My setup: alpha linux with 2 NICs (21143 and 21140). One NIC is connected
> to some TrendNet 10/100 switch (FD link), second NIC is connected to 100TX
> hub. At first, I tried to link 21140 to hub and 21143 to switch. I got
> about 1.5MBps throughput through 21143. Then I changed setup so that 21140
> is connected to switch and 21143 to hub. Now I'm getting transfers at >90%
> of wire speed on both connections. I'm using tulip.c v0.91 and kernel
> 2.2.12.
> I guess something's wrong with FD on 21143.
Just out of curiousity, I tried using the de4x5 (alternative tulip)
driver. It came up in half duplex mode by default, but TCP performance
was wore (~65Mb/s I think).

I'm not completely convinced FD is broken on the 21143. One thing I'd
like to try tomorrow is connecting the two machines directly with a
crossover cable, and setting them to 100Tx-FD. That should show whether
this is a negotiation or FD problem.

Thanks again,

David Friedman