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Date:      Mon, 04 Jun 2007 10:18:40 -0400
From:      Rob <r17fbsd@xxiii.com>
To:        FreeBSD Questions <freebsd-questions@freebsd.org>
Cc:        tundra@tundraware.com
Subject:   Re: Strange Intel Mobo Behavior
Message-ID:  <46641F40.8030508@xxiii.com>
In-Reply-To: <4663AFCC.6080508@tundraware.com>
References:  <46630382.8010901@tundraware.com>	<6.2.3.4.2.20070603232531.03dffe40@mailsvr.xxiii.com> <4663AFCC.6080508@tundraware.com>

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Tim Daneliuk wrote:
>> The ad6 drive is supposed to do SATA-300, but realistically, other 
>> bottlenecks dictate it's not going to get anywhere near the '150 speed, 
> 
> Could you comment a bit more on why you think this is so.  I would
> think that with modern processors and buses, a machine with light load
> ought to be able to drive SATA-300, but I've never actuall tested for

I was off on my initial assumptions.  I thought the "150" was 150 Giga-bit/sec, or approx 15 Giga-byte, or 15000 MB/sec.  Which is well above the PCI and other bus speeds it needs to travel through to get to the processor.

But reading http://en.wikipedia.org/wiki/Serial_ATA it's 150 Mega-byte/sec.  I think older ATA chipsets are part of the PCI bus, which at 32 bits * 33MHz, which is about a 132MB/sec bottleneck.  I don't know enough about PCI-X, PCI-E and newer chipsets to know speeds & bottlenecks, so I'll just shut up now ;)  But seems like > 100MBs should be within reach.

  -RW




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