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From: "David S. Miller" <davem@redhat.com>
To: benh@kernel.crashing.org
Cc: anton@samba.org, billfink@mindspring.com,
	linuxppc-dev@lists.linuxppc.org
Subject: Re: GigE Performance Comparison of GMAC and SUNGEM Drivers
Date: Tue, 20 Nov 2001 16:19:37 -0800 (PST)	[thread overview]
Message-ID: <20011120.161937.118616800.davem@redhat.com> (raw)
In-Reply-To: <20011121000518.8434@mailhost.mipsys.com>


   From: benh@kernel.crashing.org
   Date: Wed, 21 Nov 2001 01:05:18 +0100

   Ah, ok, I stand corrected. Is this a bug in the chip or a flaw of
   the GEM chip design ? I mean, is there a chance that later revs
   of the chip or eventually the one used by Apple can support it ?

There is no chance whatsoever of this ever working on any
GEM revision.

Even if it could work, GEM has a 9K transmit and 20K receive fifo in
the largest configuration.  Even the Acenic has 512k or 1MB of total
on-chip ram for packet buffering.

As a result GEM sends pause frames when there is even the slightest
amount of DMA traffic is has to compete with.  On a 33Mhz/32-bit PCI
bus, it is sending pause frames all the time even if it is the only
agent making use of the bus.

** Sent via the linuxppc-dev mail list. See http://lists.linuxppc.org/

  reply	other threads:[~2001-11-21  0:19 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2001-11-18  6:45 GigE Performance Comparison of GMAC and SUNGEM Drivers Bill Fink
2001-11-19  0:15 ` Anton Blanchard
2001-11-19 12:54   ` Benjamin Herrenschmidt
2001-11-20  6:34     ` Bill Fink
2001-11-20 12:02       ` Benjamin Herrenschmidt
2001-11-20 19:50         ` David S. Miller
2001-11-21  0:05           ` benh
2001-11-21  0:19             ` David S. Miller [this message]
2001-11-21  1:25               ` Benjamin Herrenschmidt
2001-11-21  4:17               ` Bill Fink
2001-11-21  3:46   ` Bill Fink
2001-11-21  5:36     ` Anton Blanchard

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