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Re: [Qemu-devel] Can you commit the pcnet patch ?

From: Fabrice Bellard
Subject: Re: [Qemu-devel] Can you commit the pcnet patch ?
Date: Thu, 21 Jul 2005 23:14:32 +0200
User-agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.3) Gecko/20040913

Paul Brook wrote:
On Thursday 21 July 2005 08:29, Lars Munch wrote:

On Wed, Jul 20, 2005 at 12:32:10PM +0200, Ludovic Drolez wrote:

Hi !

I've tried the latest AMD pcnet patch (made by Antony T Curtis) with qemu
0.7 because I was tired of the sloooww PXE booting of my QEMU. For
exemple, to load a linux kernel + initrd over TFTP, it takes 4m30s with a
ne2000, and 1m35s with the PCNET card.

Does anyone know why pcnet is so much faster than ne2000? is it easier
to emulate? or is there room for improvements on the ne2000?

Probably because it's a DMA capable controller. IIRC the ne2k is pio based, so has to shuffle the data through an IO port one byte at a time.

I don't think that the switch to DMA can explain a factor of 3. Another possibility is that there is a bug in the ne2000 code. It could be interesting to check the send and receive latencies by adding traces in the ne2000 code...


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