The repositioning of Core Ultra 200S (Arrow Lake) CPU cores to the north side of the chip – compared to the previous southern placement – has also shifted the location of the CPU’s thermal hotspot, where the most intense heat transfer is needed. Noctua has responded with the NM-IMB8a offset mounting bars, which reposition the coldplate of the NH-D15 G2 cooler on the processor to achieve lower operating temperatures.
For its highest-performance cooler, the NH-D15 G2, Noctua offers multiple variants (LBC, standard, HBC), each optimized for different platforms. The key difference lies in the curvature of the coldplate surface that makes contact with the IHS of the CPU.
Each variant’s coldplate flatness has been fine-tuned by Noctua to ensure optimal mounting pressure is applied directly over the CPU’s thermal hotspots. For this to remain true on the Intel LGA 1851 platform (Arrow Lake), Noctua had to release a new adapter that repositions the cooler relative to the CPU. That’s because, compared to 12th–14th gen Intel CPUs (LGA 1700), the hotspot has now shifted northward, which requires the coldplate contact area to adapt as well – at least if you want to extract maximum thermal performance from your cooler. This is the role of the Noctua NM-IMB8a offset mounting bars.
These are replacement bars that install in place of the default ones bundled with Noctua coolers. What changes is that the NM-IMB8a shifts the coldplate closer to the actual CPU hotspots, resulting in more effective heat transfer. While designed primarily for the NH-D15 G2, the adapter is also compatible with other coolers using a 78 mm mounting hole spacing, including the NH-L12S, NH-L12Sx77, NH-L12 Ghost S1 edition, and NH-D12L. chromax.black variants are also supported where available.
Noctua reports a temperature drop specifically when using the NH-D15 G2 on CPUs like the Core Ultra 7 265K and Core Ultra 9 285K. These are CPUs with the highest P-core counts, and they benefit the most from the NM-IMB8a’s offset installation, in terms of hotspot cooling.
These CPUs naturally generate high thermal densities, not just due to high clock speeds, but also their core counts – CU7 265K has 20 cores (8P + 12E), CU9 285K has 24 (8P + 16E). Noctua claims the HBC variant of the NH-D15 G2 can lower hotspot temperatures by up to 3 °C. This likely refers to scenarios with extreme all-core workloads on the Core Ultra 9 285K. With the “standard” variant featuring medium convexity, the improvement drops to about 1 °C, while the “LBC” variant brings only ~0.65 °C on average.
Despite HBC showing the highest gains, Noctua still considers the medium-convexity “standard” variant the most balanced option when paired with the NM-IMB8a. Although the bars yield a smaller improvement with this variant, its coldplate already achieves solid contact on LGA 1851 even without the adapter. That nuance should be taken into account when evaluating the overall cooling benefit.
The NM-IMB8a bars are available for purchase via Noctua’s online form for 3.90 EUR, or soon through Amazon for 4.90 EUR. We also expect to see them in regional retailers like Tiché PC.
English translation and edit by Jozef Dudáš
