Intel Core i9-12900K tested with overclocked DDR5-8000 RAM

Intel Core i9-12900K tested with overclocked DDR5-8000 RAM

Twitter user REHWK shared a screenshot showing the Intel Core i9-12900K processor paired with pretty fast DDR5 memory. The image, taken from CPU-Z, seems to confirm that the CPU has a TDP of 125W and an L3 cache of 30MB. We have known these specifications for some time, but it is always good to have some confirmation. What is also evident when looking at the instruction set list is that Alder Lake does not support AVX-512. While the Golden Cove cores support AVX-512, the Gracemont ones lack one and, therefore, Intel simply disabled the AVX-512 instruction set in the Golden Cove cores to maintain uniform ISA support.

Alder Lake is natively compatible with DDR4 and DDR5 memory and the default speeds supported are DDR4-3200 and DDR5-4800 respectively. The Core i9-12900K in question was tested on the Gigabyte Z690 Aorus Tachyon motherboard with the corresponding Gigabyte DDR5-4800 memory (GP-ARS32G62D5). It is plausible that the screenshot comes from an overclocker testing the limits of the DDR5 kit; therefore, a rather thorough cooling system was probably used to bring the modules to such speeds.

Photo credit: REHWK / Twitter Natively, DDR5-4800 memories have timings set to 42-39-39- 77 to just 1.1V.There are two XMP 3.0 profiles for DDR5-6200: one configures memories to 40-40-40-80 at 1.35V, while the other reduces timings to 38-38-38 -76, but increase the DRAM voltage to 1.5V. Apparently, the memory module also has a third XMP 3.0 profile for DDR5-6400 with timings of 42-42-42-84 at 1.45V.

With Rocket Lake, Intel introduced Gear mode, similar to AMD's Infinity Fabric Clock (FCLK), for memory overclocking. In short, Gear modes allowed the controller and memories to run at different frequencies. For example, Gear 1 maintains a 1: 1 ratio, while Gear 2 reduces the controller frequency by half, resulting in a 0.5: 1 ratio. A recent patch for HWiNFO64 implies that Intel will implement the same modes in Alder Lake, while a leak revealed a potential Gear 4 option to reduce the controller to a quarter of the memory frequency.

The overclocker brought the RAM from DDR5-4800 to DDR5-8000, which is an impressive 67% improvement, setting the timings to 50-50-50-100. In the screenshot, the memory controller is clocked at 2,000 MHz, while the memories are at 4,000 MHz. It is quite remarkable that the overclocker managed to achieve this in Gear 2 mode.