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From: torvalds@transmeta.com (Linus Torvalds)
Subject: Re: What's left over.
Date: Fri, 1 Nov 2002 15:25:01 +0000 (UTC)
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In article <20021031194351.GA24676@tapu.f00f.org>,
Chris Wedgwood  <cw@f00f.org> wrote:
>On Thu, Oct 31, 2002 at 10:49:10AM -0800, Linus Torvalds wrote:
>
>> Any hardware that needs to go off and think about how to encrypt
>> something sounds like it's so slow as to be unusable. I suspect that
>> anything that is over the PCI bus is already so slow (even if it
>> adds no extra cycles of its own) that you're better off using the
>> CPU for the encryption rather than some external hardware.
>
>Except almost all hardware out there that does this stuff is async to
>some extent...

That's not my argument.  I realize that external hardware on a PCI bus
_has_ to be asynchronous, simply because it is so slow. 

The question I have is whether such external hardware is even worth it
any more for any standard crypto work.  With a regular PCI bus
fundamentally limiting throughput to something like a maximum of 66MB/s
(copy-in and copy-out, and that's so theoretical that it's not even
funny - I'd be surprised if RL throughput copying back and forth over a
PCI bus is more than 25-30MB/s), I suspect that you can do most crypto
faster on the CPU directly these days. 

Maybe not. The only numbers I have is the slowness of PCI.

		Linus
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