linux-kernel - Re: RFC: outb 0x80 in inb_p, outb_p harmful on some modern AMD64 with MCP51 laptops

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Message-ID: <475E25D2.1050009@zytor.com>
Date:	Mon, 10 Dec 2007 21:53:22 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Andi Kleen <andi@...stfloor.org>
CC:	"David P. Reed" <dpreed@...d.com>, linux-kernel@...r.kernel.org,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>
Subject: Re: RFC: outb 0x80 in inb_p, outb_p harmful on some modern AMD64
 with MCP51 laptops

Andi Kleen wrote:
>> My machine in question, for example, needs no waiting within CMOS_READs 
>> at all.   And I doubt any other chip/device needs waiting that isn't 
> 
> I don't know about CMOS, but there were definitely some not too ancient
> systems (let's say not more than 10 years) who required IO delays in the
> floppy driver and the 8253/8259. But on those the jumps are already
> far too fast.
> 

Yes, early Linux used jumps.  I believe it broke a bunch of machines 
when the P5 came out, as the jumps were too fast.  (I have to admit to 
being a bit fuzzy on this... my memory says it was the 486 and not the 
P5, but that clearly can't be the case since my first Linux box was a 
486/33.)

	-hpa
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