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

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Date:	Sat, 8 Dec 2007 20:26:31 +0000
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	"David P. Reed" <dpreed@...d.com>
Cc:	Andi Kleen <andi@...stfloor.org>, linux-kernel@...r.kernel.org,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: Re: RFC: outb 0x80 in inb_p, outb_p harmful on some modern AMD64
 with MCP51 laptops

> In any case, my machine does not have an ISA bus.  Why should it?  It's 
> a laptop!

Yes it does. The branding spec said "No ISA bus" so it was renamed "LPC"
and hidden internally, but its alive and well.

> has already serviced the bus and delivered data!  Why put many 
> microseconds into the bus, locking out other ISA transactions (and PCI 
> maybe too) with an out to port 80?

Historically processors didn't have a high precision time source so it
was the normal way to do it on all PC operating systems

> Some of the code in linux is really nice, really clean, really 
> well-thought out.  Some is ... well, I'm not trolling for a fight.

Like all things, it doesn't always age well 8)
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