Date: Wed, 10 Apr 1996 17:29:24 +0930 (CST) From: Michael Smith <msmith@atrad.adelaide.edu.au> To: terry@lambert.org (Terry Lambert) Cc: Brett_Glass@ccgate.infoworld.com, terry@lambert.org, questions@FreeBSD.org Subject: Re: Artisoft AE-3 Ethernet card: How to use large buffer? Message-ID: <199604100759.RAA22630@genesis.atrad.adelaide.edu.au> In-Reply-To: <199604100104.SAA06406@phaeton.artisoft.com> from "Terry Lambert" at Apr 9, 96 06:04:34 pm
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Terry Lambert stands accused of saying:
>
> > I'm not sure, but I believe that the internal buffer is not directly
> > accessible on NE2000 clones. As I understand it, the RAM is accessible via
> > programmed I/O after setting a pointer register. (This is one of the common
> > criticisms of the architecture: PIO isn't quite as fast as shared memory.)
Brett is correct here, in that memory on the NEx000 cards is not
directly mapped.
> > > You need to set mem_end to mem_start + 64k. This should be done in
> > > whichever probe routine is coming true.
> >
> > Aren't the mem_end and mem_start parameters used for cards that have shared
> > memory (rather than a PIO/counter scheme)?
There are different I/O routines used depending on the card type; see
the ed_pio_* routines for those that work with the NEx000 cards.
> > Again, I'm not certain, but I believe that access to the buffer does not
> > take place via a memory window at all.
>
> I was reading from the comments in the /sys/i386/isa/if_ed.c. Search
> for the string "mem_end".
>
> I think you might be looking at the 3COM specific code?
No, the 3com cards have (optional) shared memory, which IIRC is required.
Regardless, mem_{start|end|size} are the correct numbers to work with,
they describe the internal configuration of the card.
> Terry Lambert
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