Defective Raptor Lake CPUs: Intel finds the root cause

It has taken more than half a year; now Intel claims to have found the root cause of the failing Raptor Lake processors of the two desktop series Core i-14000 and Core i-13000. A "clock tree circuit" within the CPU cores is said to be particularly susceptible to ageing under increased voltage and temperature and ultimately cause crashes.

In a clock tree, different clock frequencies in the chip are derived from a base frequency – not all logic areas run at the same clock frequencies. Reading between the lines, Intel's announcement sounds like the affected circuit is designed on edge. The problem is separate from a temporary manufacturing error in earlier batches.

The Core i-12000 (Alder Lake) with the same core architecture should not suffer from the problem. For notebooks, the 13000 and 14000 models should also not cause any problems – where the voltages are generally lower. Intel also promises that the upcoming Core Ultra 200 aka Arrow Lake should not be affected.

Premature ageing occurs in combination with excessive voltages, which are partly caused by the standard BIOS settings of the motherboard manufacturers and partly by Intel's own microcode. The manufacturer has now found a further point where the voltages are too high at low computing loads, which new BIOS updates are intended to rectify.

If a processor has aged too much, this manifests itself in crashes in applications and games because the CPU can no longer maintain its clock frequencies. In the worst case, the processor can no longer be used in everyday life.

BIOS updates fix several problems

In the case of the Core i-14000 and Core i-13000, it is to a certain extent a "perfect storm" of several factors that together exacerbate the problem. Intel describes a total of four problems which, taken together, explain the unusually high defect rate of the overclockable K models in particular, such as the Core i9-14900K:

1. Excessively high voltages in the BIOS settings, usually set at the factory
2. Microcode bug in the Enhanced Thermal Velocity Boost (eTVB), which causes CPUs to not lower the voltages and clock frequencies correctly at high temperatures
3. Microcode bug in the Serial Voltage Identification Debug Protocol (SVID), which leads to a shift in the Vmin voltage
4. Microcode and BIOS code request increased core voltages, which can cause a Vmin shift, especially during idle and/or low activity

Vmin is the minimum voltage at which the individual cores still work. This can vary slightly for each individual processor and is permanently set for each CPU during production tests. If this minimum voltage is too high, all other voltages for the boost functions will also be too high.

For point 4 on Vmin, Intel is once again updating its microcode to version 0x12B, which contains the corrections to 0x125 and 0x129 with the previous problem fixes and an Intel base profile for suitable voltages and power limits. Mainboard manufacturers are expected to release BIOS updates containing the new microcode in the coming weeks. According to Intel, the performance impact of the change from 0x125 to 0x12B should be marginal. The updates to version 0x125 already only had a minor impact on performance.

Intel has not yet provided a tool to determine whether a processor is running stably within the specification or tends to crash. If a CPU causes crashes, it must be replaced.

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(mma)