linux-kernel - Re: [RFT] Port 0x80 I/O speed

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Date:	Wed, 12 Dec 2007 08:23:10 -0500
From:	"linux-os (Dick Johnson)" <linux-os@...logic.com>
To:	"Rene Herman" <rene.herman@...access.nl>
Cc:	Alejandro Riveira Fernández 
	<ariveira@...il.com>,
	"Linux Kernel" <linux-kernel@...r.kernel.org>, <dpreed@...d.com>,
	"Alan Cox" <alan@...rguk.ukuu.org.uk>, <pavel@....cz>,
	<andi@...stfloor.org>, <rol@...917.net>,
	"Krzysztof Halasa" <khc@...waw.pl>, <david@...idnewall.com>,
	<hpa@...or.com>, <john@...ffel.org>
Subject: Re: [RFT] Port 0x80 I/O speed


On Wed, 12 Dec 2007, Rene Herman wrote:

> On 12-12-07 13:59, linux-os (Dick Johnson) wrote:
>
>> On Tue, 11 Dec 2007, [utf-8] Alejandro Riveira Fern?ndez wrote:
>
>>> On my AMD 3800 X2 (2000MHz) ULi M1697 2.6.24-rc5 i get:
>>>
>>> cycles: out 1844674407370808, in 1844674407369087
>>>
>>> It is not constant but variations are not significant afaics
>>>
>>
>> It looks as though this hardware does not have a port 0x80
>> and its access is trapped by the hardware with a long time-out!
>> This may be the reason when the _p was called "harmful" on this
>> platform!
>>
>> I'm not sure the "rules" for port access allow for this kind of
>> behavior. This design may be defective, needing to be brought
>> to the attention of the vendor. A decent vendor would update
>> a FPGA and provide code to burn a new BIOS.
>
> I'm afraid it's just the test that is "defective" as 64-bit code. For some
> reason "=A" doesn't mean edx:eax on amd64 even though it's a useful register
> pair to be able to name there as well. Didn't catch that being without amd64
> machines myself.
>
> Oh well. gcc -m32 fixes it...
>
> Rene.
>

Yep. By bad. I actually believed the returned value!


Cheers,
Dick Johnson
Penguin : Linux version 2.6.22.1 on an i686 machine (5588.30 BogoMips).
My book : http://www.AbominableFirebug.com/
_


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