Date: Mon, 16 Jul 2001 18:37:27 -0700 (PDT) From: Julian Elischer <julian@elischer.org> To: Soren Kristensen <soren@soekris.com> Cc: Bsdguru@aol.com, hackers@FreeBSD.ORG Subject: Re: NatSemi DP83820 gigE driver kit for 4.2 and 4.3 Message-ID: <Pine.BSF.4.21.0107161836400.84815-100000@InterJet.elischer.org> In-Reply-To: <3B532A40.6BC65369@soekris.com>
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The proble is that teh ethernet header is 14 bytes so you must choose to allighn either the whole packet, or the IP header, but you cannot do both. On Mon, 16 Jul 2001, Soren Kristensen wrote: > Hi, > > Bsdguru@aol.com wrote: > > > > In a message dated 07/16/2001 1:11:09 PM Eastern Daylight Time, > > tlambert2@mindspring.com writes: > > > > > > How do these perform compared to the more expensive gigabit cards? > > > > > > Read the driver. > > > > > > In general, they require an extra copy because of the inability > > > of the card to DMA on a reasonable boundry. > > > > > > Bill's commentary in his drivers is frequently enlightening, > > > and often amusing... 8-). > > > > > > > Maybe at some point he'll "get" that the boundry issue is a pci bus-mastering > > spec issue and not a controller design flaw, as he seems to harp on this in > > just about every driver? > > That's incorrect, there no nothing limiting a PCI device for doing > busmastering on a byte boundary.... The reason why not that many devices > support it, especially on the receive side, is that the circuit gets > more complicated. > > Another thing, since there is all this hardware that requires alignment, > maybe we should consider modifying FreeBSD so receive buffers are > aligned, afaik, Linux use aligned receive buffers.... But I don't know > how complicated that would be, so please don't flame me :-) > > > A more important question is "are these 32-bit cards, and if so, do they have > > enough internal buffer to do sustained 1GB transfers". Generally 32-bit PCI > > is too slow for GB, as it cant do sustained 1GB transfers. Some 32-bit GB > > cards are just a total waste. > > > > > Soren > > To Unsubscribe: send mail to majordomo@FreeBSD.org > with "unsubscribe freebsd-hackers" in the body of the message > To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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