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Date:      Wed, 5 Nov 2003 09:23:47 -0500 (EST)
From:      Andrew Gallatin <gallatin@cs.duke.edu>
To:        Fred Clift <fclift@verio.net>
Cc:        freebsd-alpha@freebsd.org
Subject:   Re: Miata MX5 and 64 bit gigabit ethernet
Message-ID:  <16297.2035.310311.968335@grasshopper.cs.duke.edu>
In-Reply-To: <20031104155314.W3281@irfcn.qzm.berz.irevb.arg>
References:  <20031102022925.W28113@loafier.com> <20031104155314.W3281@irfcn.qzm.berz.irevb.arg>

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Fred Clift writes:

 > If the card does dma, then it will be unlikley to work.  I dont know that
 > Gigabit ethernet existed when miatas were new, and hence, DEC wouldn't

Please get a clue or stop spreading FUD.  

The DMA bug occurs when crossing a page (8K) boundary using scatter/gather
DMA READs.  FreeBSD doesn't even use scatter/gather for anything but
ISA cards at the moment.  Most GigE cards are not ISA ;)

For what its worth,  we used Alteon Tigon II Gigabit nics on our
Miatas back when the hardware was current and 4.0 was -CURRENT.

Even if it works, don't expect great performance.  As best as I can
remember, we never managed to get much more than 500Mb/sec throughput,
even with jumbo frames.  This is partly because the Miata's PCI bus /
memory system really sucks by modern standards and it can't get
anywhere near the 250MB/sec theoretical PCI max...


Drew



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