linux-kernel - Re: [RFT] Port 0x80 I/O speed

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Date:	Wed, 12 Dec 2007 01:27:30 +0100
From:	Rene Herman <rene.herman@...il.com>
To:	Maxim Levitsky <maximlevitsky@...il.com>
CC:	Linux Kernel <linux-kernel@...r.kernel.org>, dpreed@...d.com,
	Alan Cox <alan@...rguk.ukuu.org.uk>, pavel@....cz,
	andi@...stfloor.org, rol@...917.net,
	Krzysztof Halasa <khc@...waw.pl>, david@...idnewall.com,
	hpa@...or.com, john@...ffel.org, linux-os@...logic.com
Subject: Re: [RFT] Port 0x80 I/O speed

On 12-12-07 01:14, Maxim Levitsky wrote:

> CPU frequency locked to 2128.000 Mhz:
> maxim@...N:~/tmp$ sudo ./port800
> cycles: out 1650, in 1065

> CPU frequency locked to: 1596.000 Mhz
> maxim@...N:~/tmp$ sudo ./port800
> cycles: out 1730, in 1138

> A bit strange, isn't it?

Well, yes. Don't know what that effect is. A bus-clock divided from the CPU 
clock comes to mind, but I believe that shouldn't happen to LPC.

Anyways, we're looking for an upper bound and that's still nicely below 2 us 
on everything upto now, so I guess it doesn't matter all that much. Thanks!

Rene.
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