linux-kernel - Re: [PATCH] floppy: revert floppy disable halt warning

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Message-ID: <20120328114627.51b64541@pyramind.ukuu.org.uk>
Date:	Wed, 28 Mar 2012 11:46:27 +0100
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Ingo Molnar <mingo@...nel.org>, Josh Boyer <jwboyer@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Stephen Hemminger <shemminger@...tta.com>,
	Len Brown <len.brown@...el.com>, linux-kernel@...r.kernel.org,
	Ingo Molnar <mingo@...e.hu>
Subject: Re: [PATCH] floppy: revert floppy disable halt warning

On Wed, 28 Mar 2012 00:20:46 -0700
"H. Peter Anvin" <hpa@...or.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


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