Problem with realtime on PC

Probably an SMI : System Management Interrupt => non maskable. We had to tackle the same problem for our RT application.

Check in setup fro a parameter like "thermal delay " or dont remember the name and affect it the smallest possible value like 4 minute => after that delay, the SMI does not occur anymore.

I think it is possible to really handle the problem with the Pentium MSR (model specific registers) .

Most likely, SMI's. It's just been discussed:

-- Cyril

Cyril Novikov wrote: : On 05.06.2006 14:39, Slavisa Zigic wrote: :> Hello, :> :> I am using AAEON motherboards, models MB-845GE and EMB-845GE. The system is :> hard real time where response is expected in few microseconds. I tried :> running different software, but no matter what I am running, there is :> "dead-time" of approximately 250 us. This means that every few minutes, CPU :> will stop executing program for 250 us and then continue. I tried two :> different CPUs, P4 at 2.8 and 1.7GHz and both are showing the same problems. :> I also tried the same CPUs in two motherboards from different manufacturers :> and there is no "dead-time" on CPU. The only common thing on two different :> motherboards is the same Intel 845GE chipset. I also found that PROCHOT# pin :> on CPU is always asserted (logic '0'). I am running all tests on DOS :> platform (no multitasking). :> It doesn't matter if you enable/disable interrupts or enable disable APIC. :> Any idea what is causing this?

: Most likely, SMI's. It's just been discussed:

:

: -- : Cyril

Cyril,

I downloaded 845GE chipset datasheet and wrote a small program to read control/status registers. All registers in South Bridge have default settings, which means, SMI disabled.

Now, about MSR on Pentium... Do I have to write routine in assembly (inline, if I use gcc) or there is C library available for MSR access?

Thanks,

Slavisa Zigic

I disabled Thermal Management (TM1 & TM2) by writing 0x81 to IA32_MISC_ENABLE. Bit 3 is Thermal Monitor 1 (TM1) enable, bit 13 is Thermal Monitor 2 (TM2) enable.

Nothing changed regarding 250us CPU stall.

Slavisa Zigic

Slavisa Zigic wrote: : Cyril Novikov wrote: : : On 05.06.2006 14:39, Slavisa Zigic wrote: : :> Hello, : :> : :> I am using AAEON motherboards, models MB-845GE and EMB-845GE. The system is : :> hard real time where response is expected in few microseconds. I tried : :> running different software, but no matter what I am running, there is : :> "dead-time" of approximately 250 us. This means that every few minutes, CPU : :> will stop executing program for 250 us and then continue. I tried two : :> different CPUs, P4 at 2.8 and 1.7GHz and both are showing the same problems. : :> I also tried the same CPUs in two motherboards from different manufacturers : :> and there is no "dead-time" on CPU. The only common thing on two different : :> motherboards is the same Intel 845GE chipset. I also found that PROCHOT# pin : :> on CPU is always asserted (logic '0'). I am running all tests on DOS : :> platform (no multitasking). : :> It doesn't matter if you enable/disable interrupts or enable disable APIC. : :> Any idea what is causing this?

: : Most likely, SMI's. It's just been discussed:

: :

: : -- : : Cyril

: Cyril,

: I downloaded 845GE chipset datasheet and wrote a small program to read : control/status registers. All registers in South Bridge have default : settings, which means, SMI disabled.

: Now, about MSR on Pentium... : Do I have to write routine in assembly (inline, if I use gcc) or there : is C library available for MSR access?

: Thanks,

: Slavisa Zigic

After disabling TCO_EN SMI#, problem disappeared.

The only question now is: Are there any side effects?

When you disable all devices than can assert SMI# to CPU, is there any danger of overheating CPU or any other part on the motherboard?

Thanks,

Slavisa Zigic

Slavisa Zigic wrote: : I disabled Thermal Management (TM1 & TM2) by writing 0x81 to : IA32_MISC_ENABLE. Bit 3 is Thermal Monitor 1 (TM1) enable, bit 13 is Thermal : Monitor 2 (TM2) enable.

: Nothing changed regarding 250us CPU stall.

: Slavisa Zigic

: Slavisa Zigic wrote: : : Cyril Novikov wrote: : : : On 05.06.2006 14:39, Slavisa Zigic wrote: : : :> Hello, : : :> : : :> I am using AAEON motherboards, models MB-845GE and EMB-845GE. The system is : : :> hard real time where response is expected in few microseconds. I tried : : :> running different software, but no matter what I am running, there is : : :> "dead-time" of approximately 250 us. This means that every few minutes, CPU : : :> will stop executing program for 250 us and then continue. I tried two : : :> different CPUs, P4 at 2.8 and 1.7GHz and both are showing the same problems. : : :> I also tried the same CPUs in two motherboards from different manufacturers : : :> and there is no "dead-time" on CPU. The only common thing on two different : : :> motherboards is the same Intel 845GE chipset. I also found that PROCHOT# pin : : :> on CPU is always asserted (logic '0'). I am running all tests on DOS : : :> platform (no multitasking). : : :> It doesn't matter if you enable/disable interrupts or enable disable APIC. : : :> Any idea what is causing this?

: : : Most likely, SMI's. It's just been discussed:

: : :

: : : -- : : : Cyril

: : Cyril,

: : I downloaded 845GE chipset datasheet and wrote a small program to read : : control/status registers. All registers in South Bridge have default : : settings, which means, SMI disabled.

: : Now, about MSR on Pentium... : : Do I have to write routine in assembly (inline, if I use gcc) or there : : is C library available for MSR access?

: : Thanks,

: : Slavisa Zigic