linux-kernel - Re: x86_64 ten times slower than i386

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Date:	Sat, 3 Nov 2007 11:26:40 -0500
From:	Matt Mackall <mpm@...enic.com>
To:	Bo Brant?n <bosse@....umu.se>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: x86_64 ten times slower than i386

On Sat, Nov 03, 2007 at 01:31:49PM +0100, Bo Brant?n wrote:
> 
> Hello,
> 
> I tryed different linux distributions on a computer with an Intel Core 2 
> Quad and I noticed that the 64-bit versions was at least 10 times slower 
> than the 32-bit versions, to boot the system took over 20 minutes in 64-bit 
> mode and then even scrolling text at the command prompt felt slow, however 
> Vista 64 boots as fast as Vista 32 on the same computer. So I would like to 
> ask if this is a known problem or if there is some simple misstake I can 
> have done.
> 
> I used live cd's from gentoo and ubunto and at least ubuntu has a rather 
> new kernel, also dmesg doesn't show anything strange, for example is the 
> bogomips figure the same as when booting in 32-bit mode.

This is typically due to a problem with the setup of your MTRRs. Try
booting with mem=nnnM where nnn is some number smaller than your
actual amount of memory.

-- 
Mathematics is the supreme nostalgia of our time.
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