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Date: Wed, 27 Jul 2005 13:28:52 -0400
From: Gary Mu1der <gmulder@infotechfl.com>
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Subject: Re: Tyan S2885 Thunder K8W lockups
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Gary Jennejohn wrote:
> NAKATA Maho writes:
> 
>>How to lockup:
>># dd if=/dev/mem of=/dev/null bs=1024k
>>about 50 seconds later it lockups. 100% reproducible.
>>* Both Optimal/Failsafe setting in BIOS
>>* Both MTRR Mapping Continuous/Disabled
>>* set hw.physmem="4G" doesn't help
>>
>>workaround:
>>on board GbE (bge0) and SATA disabled.
>>
>>any hints or comments?
>>
> 
> 
> I could be wrong, but it seems to me that you might be accessing HW
> address space with resulting undesirable side effects since you're
> trying to read the entire range which /dev/mem maps.

I can confirm I tried the same thing and got the same result with 
similar hardware.

It was also pointed out to me that reading indiscriminately from 
/dev/mem may screw up memory mapped I/O and likely cause a crash.

Gary