Date: Mon, 03 Apr 1995 15:45:55 -0700 From: David Greenman <davidg@Root.COM> To: Luigi Rizzo <luigi@labinfo.iet.unipi.it> Cc: hackers@FreeBSD.org Subject: Re: NE2000 Plus performance Message-ID: <199504032246.PAA02907@corbin.Root.COM> In-Reply-To: Your message of "Mon, 03 Apr 95 09:18:02 %2B0200." <199504030718.JAA09037@labinfo.iet.unipi.it>
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>> It's not supported. I didn't even know of the NE2000+ existence until you >> mentioned here. > >Ok. A couple of questions about network ards and drivers, though: > >1) how much faster are memory-mapped cards wrt io-mapped ones ? Is it > just the clock cycle per word that you save in transferring data > with MOVSW instead of INSW, or there is more (e.g. the driver > does more or less random access to the board, thus has to waste > time specifying the address of the desired data quite often) ? SMC cards have shared memory that can be read and written at 4MB/sec. The NE2000 style cards (using programmed I/O) transfer bytes at about 1.7MB/sec. Thus when trying to do 1100KB/sec, the SMC cards take 25% of the CPU to read/write the packet and the NE2000 cards take more than 60% of the CPU. >2) not long ago,, if memory serves, it was mentioned that the > network drivers in freebsd use only one buffer for tx data, and > the rest of the memory for rx packets. If this is true, how can It isn't true for if_ed.c (the driver for the cards we're talking about). It's also not true for most of the other supported cards. The 'ed' driver uses a multi buffering scheme to transmit packets if the card has 16K or more of memory...this includes SMC 16bit cards, NE2000's, and 16bit 3c503's. -DG
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