disabling SMI

*** rampant top-posting fixed ***
Slavisa Zigic wrote:
> In comp.realtime Slavisa Zigic <szigic@nyx.net> wrote:
>> <Larry.Martell@gmail.com> wrote:
>>> Armin Steinhoff wrote:
>>>> Larry.Martell@gmail.com wrote:
>>>>
>>>>> I have a real-time app that runs on a P4. The box we are running
>>>>> it on has an Aopen  i865PEa-7IF motherboard. We are using the
>>>>> On-Time RTOS. We have found that every 37 seconds the app
>>>>> completely stops running for 250 microseconds. Using a PCI bus
>>>>> analyzer we discovered that between the last operation done by
>>>>> my app and when my app resumes running shows 100's and 100's of
>>>>> I/O reads and writes to addresses B3, EB, and 61. Googling on
>>>>> this has led me to believe that these accesses are related to
>>>>> SMI's and SMM. I have disabled everything in the BIOS - USB,
>>>>> LAN, power management, serial and parallel ports, modem,
>>>>> firewire, MIDI and game ports - yet my app still stops and I
>>>>> still see these accesses.
>>>>>
>>>>> Does anyone know how I can totally disable the SMI's?
>>>>
>>>> https://mail.rtai.org/pipermail/rtai/2005-July/012391.html
>>>> http://www.mail-archive.com/xenomai-help@gna.org/msg01507.html
>>>
>>> The code at this link is for the AMD Geode GX-1. It is not
>>> applicable to the P4.
>> 
>> I also have a real-time app that runs on P4. It is running on
>> AAEON MB-845GE motherboard. CPU stalls for 250us for unknown
>> reason. This event is not periodic, sometimes it is after less
>> than a minute, sometimes you have to wait for few minutes.
>> Motherboard is using Intel 845GE chipset. I downloaded datasheet
>> for South Bridge and wrote small program to read SMI enable
>> registers. All values are default (as specified in datasheet),
>> that is, SMI disabled.
>>
>> After that, I disabled Thermal Monitor on CPU (TM1 & TM2) by
>> writing to MSR IA32_MISC_ENABLE (bits 3 and 13). No change.
>> Still have 250us stall.
>>
>> 'cli' did not help, disabling APIC didn't help, disabling ALL
>> interrupts on PIC didn't help, writing to Intel Software
>> Developers Forum didn't help...
> 
> I found a way to disable SMI. Furthermore, I found that TCO_EN
> bit is causing SMI#. I am using Intel 82801DB ICH4.
> 
> How safe it is to disable SMIs?  Is there any problem with
> overheating of CPU or any other side effect?

Since this thread seems to contain valuable information, I have
gone to the trouble of correcting the top-posting and making it
readable.  It is much easier to just avoid top-posting in the first
place.  Your answer belongs after, or intermixed with, the material
to which you reply.

-- 
 "Our enemies are innovative and resourceful, and so are we. 
  They never stop thinking about new ways to harm our country
  and our people, and neither do we."          -- G. W. Bush.
 "The people can always be brought to the bidding of the
  leaders.  All you have to do is tell them they are being
  attacked and denounce the pacifists for lack of patriotism
  and exposing the country to danger. It works the same way
  in any country."                         --Hermann Goering.

CBFalconer wrote:
> *** rampant top-posting fixed ***
> Slavisa Zigic wrote:
> > In comp.realtime Slavisa Zigic <szigic@nyx.net> wrote:
> >> <Larry.Martell@gmail.com> wrote:
> >>> Armin Steinhoff wrote:
> >>>> Larry.Martell@gmail.com wrote:
> >>>>
> >>>>> I have a real-time app that runs on a P4. The box we are running
> >>>>> it on has an Aopen  i865PEa-7IF motherboard. We are using the
> >>>>> On-Time RTOS. We have found that every 37 seconds the app
> >>>>> completely stops running for 250 microseconds. Using a PCI bus
> >>>>> analyzer we discovered that between the last operation done by
> >>>>> my app and when my app resumes running shows 100's and 100's of
> >>>>> I/O reads and writes to addresses B3, EB, and 61. Googling on
> >>>>> this has led me to believe that these accesses are related to
> >>>>> SMI's and SMM. I have disabled everything in the BIOS - USB,
> >>>>> LAN, power management, serial and parallel ports, modem,
> >>>>> firewire, MIDI and game ports - yet my app still stops and I
> >>>>> still see these accesses.
> >>>>>
> >>>>> Does anyone know how I can totally disable the SMI's?
> >>>>
> >>>> https://mail.rtai.org/pipermail/rtai/2005-July/012391.html
> >>>> http://www.mail-archive.com/xenomai-help@gna.org/msg01507.html
> >>>
> >>> The code at this link is for the AMD Geode GX-1. It is not
> >>> applicable to the P4.
> >>
> >> I also have a real-time app that runs on P4. It is running on
> >> AAEON MB-845GE motherboard. CPU stalls for 250us for unknown
> >> reason. This event is not periodic, sometimes it is after less
> >> than a minute, sometimes you have to wait for few minutes.
> >> Motherboard is using Intel 845GE chipset. I downloaded datasheet
> >> for South Bridge and wrote small program to read SMI enable
> >> registers. All values are default (as specified in datasheet),
> >> that is, SMI disabled.
> >>
> >> After that, I disabled Thermal Monitor on CPU (TM1 & TM2) by
> >> writing to MSR IA32_MISC_ENABLE (bits 3 and 13). No change.
> >> Still have 250us stall.
> >>
> >> 'cli' did not help, disabling APIC didn't help, disabling ALL
> >> interrupts on PIC didn't help, writing to Intel Software
> >> Developers Forum didn't help...
> >
> > I found a way to disable SMI. Furthermore, I found that TCO_EN
> > bit is causing SMI#. I am using Intel 82801DB ICH4.
> >
> > How safe it is to disable SMIs?  Is there any problem with
> > overheating of CPU or any other side effect?

Depending on the specific MB, disabling SMI's could cause USB, power
management, audio, on-board NIC, MIDI, and joystick interfaces to not
work. On my platform (an Aopen i865PEa-7IF) the USB and NIC are still
working, and the other things are not needed by my app.

> Since this thread seems to contain valuable information, I have
> gone to the trouble of correcting the top-posting and making it
> readable.  It is much easier to just avoid top-posting in the first
> place.  Your answer belongs after, or intermixed with, the material
> to which you reply.

Thanks for doing this. Top-posting drives me crazy!

-larry