Re: Prism2 Host AP - new release 2002-04-05

From: Jouni Malinen (
Date: 2002-04-08 20:48:07 UTC

On Sun, Apr 07, 2002 at 07:01:21PM +0200, Bjørn Mork wrote:

> This made me optimistic since I've had a small performance problem
> with the latest releases (losing packets when transmitting many of
> them, causing TX speed to drop and reducing TX performance to a
> fraction of the theoretical). I'm using the driver on a 66 MHz 486
> with a Vadem ISA-PCMCIA controller, so interrupt latency is probably
> as high as it can get.

I just tested the latest version on 486 DX/4 75 MHz laptop with Intel i82365sl B step rev 00 ISA-to-PCMCIA and D-Link DWL-650 and did not run into any problems.. Which Prism2 card are you using and which firmware version?

> I guess the problem is that the platform is too slow handling the
> packets, not really that they are lost in the air. Probably not much
> that can be done about that. Your changelog made me a bit optimistic,
> but I couldn't really notice any improvement. The TX performance is
> still terrible (~500 kbits/s as opposed to the RX speed of ~5 Mbits/s).

Is that ~500 kbps TCP or UDP traffic? If it was TCP, numerous reset attempts will certainly harm the performance.

I was able to about 6 Mbps TX (and RX) speeds (UDP; about 5 Mbps with TCP) with a bit faster CPU. This was both with busy waiting command completion and interrupt version. There were not much difference in transmit rate between the versions, but system load was considerably lower with interrupt version as expected.

The driver did not log even a single dropped frame no matter what I did. I tried compiling with a lot of swapping (that laptop has only 8 megs of RAM) on the background while flooding the net, but no problems what so ever with the traffic..

I did not use bridging and the traffic went directly between the AP and the station. Did you use another NIC during the tests (i.e., interrupts both from wireless and wired card)?

Jouni Malinen                                            PGP id EFC895FA

This archive was generated by hypermail 2.1.4.