Intel, that's why Rocket Lake CPUs won't work on many 400 series motherboards
Credit: Chiphell The first reason the incompatibility would reside in the chipset. Intel's 400 series desktop family consists of six chipsets: Z490, W480, Q470, H470, B460, and H410. In turn, the Z490, W480, Q470 and H470 chipsets form the Comet Lake PCH-H group, while the B460 and H410 chipsets belong to the Comet Lake PCH-V group. As the author explained, each processor has a CPU_ID that the chipset uses to identify the chip. Logically, the processor will fail if the chipset does not recognize the CPU_ID. Apparently, the workaround is simple and is to disable CPU_ID in the Intel Management Engine (ME) section of the BIOS. Motherboard vendors, such as Gigabyte, have found a more elegant solution which consists in inserting a different chipset into H410 motherboards, as we reported yesterday.
The BIOS also plays an important role in processor support. If the processor microcode is not in the database, the chip will obviously not work on the motherboard. It is possible that Intel had already decided that the Comet Lake PCH-V chipsets would not support Rocket Lake, so the processors were not taken into consideration when developing the BIOS. Again, the solution would be to extract the microcode from the BIOS of a Z590 motherboard and insert it into another motherboard. The last, and arguably most important, reason why Rocket Lake processors are excluded from 400 series motherboards has to do with the power supply subsystem, whose job is to convert 12V and 5V voltages to lower voltages. that the processor can use. In this case, we have voltages such as Vcore (core), Vgt (core display), VCCSA, VCCIO, VCCM, VCCST, VCCST_PLL, just to name a few.
Credit: Chiphell Credit: Chiphell According to the Dell investigation 'author, Comet Lake-S and Rocket Lake-S processors did not undergo any changes in Vcore and Vgt, unlike VCCSA and VCCIO voltages. Taking an example, the forum user analyzed the ASRock Z590 Pro4 motherboard to find the Reneas RAA229001 controller that controls the VCCSA voltage. The previous VCCSA controller, which operated in fixed mode, featured a single-phase PWM with a single-phase MOS and sometimes shared with the VCCIO. With Rocket Lake-S, Intel apparently changed the power delivery mode of the VCCSA to SVID. The author explained that the supply voltage is the same as the Vcore, so the processor controls it directly. Consequently, it is not possible to share the power delivery or use another PWM. Of course, you need a PWM IC compliant with Intel's IMVP8 specification. Motherboards without a PWM SVID controller cannot accommodate Rocket Lake-S chips.
As for the VCCIO, two circuit diagrams were shared in the post that compare B460 and Z590 motherboards. Based on the author's observations, the VCCIO for Rocket Lake-S is divided into three parts. Unfortunately, on the B460 motherboard there are no connection lines to VCCIO_1_2. For reasons, which probably have to do with cost reduction, the RSVD pins for the B460 and H410 motherboards are empty, so there is no power to VCCIO_1_2. The author has provided a list of Z490 motherboards that he claims will not support Rocket Lake chips, including MSI's Z490 S01 and Z490M S01 and ASRock's Z490 Phantom Gaming 4 and Z490 Pro4.
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