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Date:      Wed, 2 Aug 2000 12:46:43 +0200 (CEST)
From:      Paul Herman <pherman@frenchfries.net>
To:        Siegbert Baude <siegbert.baude@gmx.de>
Cc:        "freebsd-questions@freebsd.org" <freebsd-questions@FreeBSD.ORG>
Subject:   Re: Realtek 8139 and DMA?
Message-ID:  <Pine.BSF.4.21.0008021240330.275-100000@bagabeedaboo.security.at12.de>
In-Reply-To: <39875E9A.8B9DB8C7@gmx.de>

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On Wed, 2 Aug 2000, Siegbert Baude wrote:

> in LINT I found the hint, that Realtek 8139 is by default in PIO-mode
> instead of DMA, because of problems with SMP-machines.
> So I commented out:
> 
> /* #define RL_USEIOSPACE */ 

From /usr/src/sys/pci/if_rl.c:

/*
 * The RealTek 8139 PCI NIC redefines the meaning of 'low end.' This is
 * probably the worst PCI ethernet controller ever made, with the possible
 * exception of the FEAST chip made by SMC. The 8139 supports bus-master
 * DMA, but it has a terrible interface that nullifies any performance
 * gains that bus-master DMA usually offers.
 *

...so it may not even be worth it.  If you *still* insist on using DMA
mode, then I would refer you to Bill Paul, who wrote the driver for
the RealTek card.

Anyway, after reading the comments in the source, I personally
wouldn't trust the DMA mode on a production server.

-Paul.



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