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From: Brian Gerst <bgerst@didntduck.org>
To: Kathy Frazier <kfrazier@mdc-dayton.com>
Cc: Andi Kleen <ak@muc.de>, linux-kernel@vger.kernel.org
Subject: Re: Interrupt doesn't make it to the 8259 on a ASUS P4PE mobo
Date: Tue, 15 Jul 2003 13:06:19 -0400	[thread overview]
Message-ID: <3F14348B.4050606@didntduck.org> (raw)
In-Reply-To: <PMEMILJKPKGMMELCJCIGOEKNCCAA.kfrazier@mdc-dayton.com>

Kathy Frazier wrote:
> Thanks for your reply, Andi.
> 
> 
>>>We have a proprietary PCI board installed in a (UP) system with an ASUS
> 
> P4PE
> 
>>>motherboard (uses Intel 845PE chipset). This system is running Red Hat
> 
> 9.0
> 
> 
>>Have you checked the 845 errata sheets on the Intel website?
>>Perhaps it is some known hardware bug.
> 
> 
>>One thing you could try is to use Local APIC / IO APIC interrupt processing
>>instead of 8259.
> 
> 
> Our hardware engineer has combed the Intel and ASUS websites, but found
> nothing.  I'll give the APIC a try and see if I get different results and
> let you know.
> 
> 
>>>/* start timer */
>>>dmatimer.expires = jiffies + 0.5*HZ;
> 
> 
>>That's a serious bug. You cannot use floating point in the kernel.
>>It will corrupt the FP state of the user process.
> 
> 
> HZ on the INTEL platform is 100, so this should simply add 50 to the current
> value of jiffies.  Besides, assigning the value to the unsigned int field
> (expires) will truncate it to an integer anyway.

Use HZ/2 instead.  GCC doesn't optimize floating point constants to the 
same degree it does integers, because it doesn't know what mode 
(rounding, precision) the FPU is in.

--
				Brian Gerst


  parent reply	other threads:[~2003-07-15 16:51 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <m3el0stw23.fsf@averell.firstfloor.org>
2003-07-15 16:14 ` Kathy Frazier
2003-07-15 15:31   ` Richard B. Johnson
2003-07-15 15:58     ` SCSI ATA driver in 2.4.22 ? Jeff Mock
2003-07-15 16:14       ` Jeff Garzik
2003-07-15 17:06   ` Brian Gerst [this message]
2003-07-15 17:43     ` Interrupt doesn't make it to the 8259 on a ASUS P4PE mobo Jamie Lokier
2003-07-15 17:59     ` Luciano Miguel Ferreira Rocha
2003-07-15 18:24       ` Brian Gerst
2003-07-15 18:44         ` Alan Cox
2003-07-15 19:44           ` Jamie Lokier
2003-07-20 21:04           ` Riley Williams
2003-07-20 22:25             ` Jeremy Fitzhardinge
     [not found] <Pine.LNX.4.53.0307141833190.4354@chaos>
2003-07-15 16:52 ` Kathy Frazier
2003-07-14 21:35 Kathy Frazier

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