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Date: Wed, 28 Mar 2012 11:46:27 +0100
From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@kernel.org>, Josh Boyer <jwboyer@gmail.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Stephen Hemminger <shemminger@vyatta.com>,
        Len Brown <len.brown@intel.com>, linux-kernel@vger.kernel.org,
        Ingo Molnar <mingo@elte.hu>
Subject: Re: [PATCH] floppy: revert floppy disable halt warning
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On Wed, 28 Mar 2012 00:20:46 -0700
"H. Peter Anvin" <hpa@zytor.com> wrote:

> On 03/27/2012 11:40 PM, Ingo Molnar wrote:
> > 
> > No objections from me.
> > 
> > Please resubmit against latest -tip, we unified the idle 
> > routines which likely interacts with that patch.
> > 
> 
> To the best of my knowledge, no-hlt only existed because of flaky power
> distributions on 386/486 systems which were sold to run DOS.  Since DOS
> did no power management of any kind, including HLT, the power draw was
> fairly uniform; when exposed to the much higher noise levels you got
> when Linux used HLT caused some of these systems to fail.

Also for the Cyrix 5510 which tended to go castors up if a HLT occurred
during a DMA cycle and on a few other boxes HLT during DMA tended to go
astray.

Do we care ? I doubt it. The 5510 was pretty obscure, the 5520 fixed it,
the 5530 is probably the oldest still in any kind of use.

Alan