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Xeon D1548 (GG8067402569300 SR2DJ) CORE 0 Clock Degraded to 800MHz due to External PROCHOT




We are facing a field Issue related to the performance degradation, we had noticed the core 0 clock degraded to the 800MHz,
This problem occurs after few days. After the initial level debugging we got to know by reading MSR_CORE_PERF_LIMIT_REASONS = e009a001,
as per the Register description when bit 0 set it means there is an External PROCHOT activated due to this core 0 clock degraded,
Now How do we debug this? we saw there is no rise in temperature and this situation persists until reboot.

Below is what we tried to read:

cpu0: PKG Limit #1: ENabled (45.000000 Watts, 1.000000 sec, clamp ENabled)
cpu0: PKG Limit #2: ENabled (54.000000 Watts, 0.007812* sec, clamp ENabled)
cpu0: DRAM Limit: DISabled (0.000000 Watts, 0.000977 sec, clamp DISabled)
cpu0: MSR_IA32_TEMPERATURE_TARGET: 0x00681600 (104 C)
cpu0: MSR_IA32_PACKAGE_THERM_STATUS: 0x8832000c (54 C)
cpu0: MSR_IA32_PACKAGE_THERM_INTERRUPT: 0x00000003 (104 C, 104 C)
CoreTmp   PkgTmp     PkgWatt       RAMWatt       PKG_%       RAM_%
54                  54              18.85              3.86            100.02         3.01

We are using Xeon D1548 (Intel P/N: GG8067402569300 SR2DJ),
480GB SSD (Swissbit AG P/N: SFSA480GM6AA4TO-C-OC-616-G30 and 2 X 16GB DIMM (Smart Modular P/N: SHB722G8CIE24KP2SB).


After a few analysis, we got to know this is happened because of assertion of the "FM_THROTTLE" signal which is coming from the processor PIN NO. - BN2 (SATA4GP_GPIO16).

And this FM_THROTTLE asserts the PROCHOT_N coming to PIN NO. - AG71 through CPLD logic and this logic is simply assets the PROCHOT when FM_THROTTLE asserted.

Now, We need to know why this FM_THROTTLE asserted as all the temperatures are normal inside and outside of processor. The only thing remains Power related or something false triggering, as per BIOS code we see in FITc tool this FM_THROTTLE pin configured in its NATIVE functions(i.e SATA4GP) so how we can be sure, this pin is actually asserted on the event which requires throttling of the cores?

One Doubt: We don't found the pin BN2 (SATA4GP_GPIO16) is using for FM_THROTTLE in any documents.


Thanks In advance


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Hello,  @GirishCiena 


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