Why VRM Matters for Z390
The CPU voltage regulator module on the motherboard is responsible for taking in 12v from the main PSU and then reducing it to anywhere from 1.2-2.0v for the CPU to utilize. With the Z390 chipset, most motherboard vendors improved their power delivery and some did not make any changes. GIGABYTE significantly improved power delivery on their motherboards. The VRM from boards as affordable as the Aorus Elite up to the Aorus Xtreme all use integrated power stages.
However, the Z390 Aorus Master and Z390 Aorus Xtreme use VRMs that cost more than twice as much as the VRMs found on the Pro and Elite series motherboard, which already have pricey high performance VRMs. The VRMs on these two boards utilize the latest in digital PWM technology from Infineon/IR and use power stages that are much smarter, with features such as internal current detection. They are also doubled up from base PWM channels to improve performance in high load situations. Why would GIGABYTE do this for their Z390 motherboards?
In Semptember 2017, before Z370 launch time, Intel released Power Supply Design Guide version 1.41. Then in June 2018, right before Z390 launch, Intel published version 1.42. We can clearly see that the 95W SKUs have had a large increase in 12v current. Calculating "SoC" (CPU) power using Intel's VRM efficiency and minimum 12v rail voltage plugged into the equation we can find the changes. They increase sustained current from 16A to 22A and peak current from 18A to 29A. Doing the math using the provided equation and operating conditions, sustained "SoC" power draw went from 155W to 210W. Peak SoC power went from 174W to 280W, which would make sense because the 9900K compared to the 8086K has two more cores, a 400MHz higher all core turbo, while it sports a base clock 400MHz lower (TDP basically). The CPU isn't magic, it's science. Now, you might be asking yourself, maybe Intel was describing overclocked CPUs?
Nah, they even went ahead and added in a section to the new power supply design guide, telling vendors that those numbers from that table above are not for overclocking, and that they will need to overdesign to support overclocking. Now, while this is all about the power supply in your case and not really about your VRM or CPU, Intel did indicate something in the 9900K's data sheet.
In the IA core ICC Max section (max current), they increased current from 138A to 193A for the 9900K, that's almost 200A, which hasn't even been multiplied by voltage to get voltage in our simplistic Ohm's law equation. So let us say my CPU runs at 1.15v at stock, the VRM would be expected to provide roughly 220W to the CPU, which matches the increased "SoC" power numbers in the power supply design document. Bottom line; the new 9th generation of CPUs are very fast, powerful, and can run on the warmer side of things, but if you want it to play nice, you need a strong VRM now more than ever. It's almost like the X299 fiasco with throttling VRMs, but to a slightly lesser extent. GIGABYTE asked us to toss its board against a very popular competitor motherboard that costs the same and is the GIGABYTE Z390 Aorus Master's direct competitor. So, we present the thermal battle at $289.
Last updated: Nov 22, 2019 at 12:49 pm CST
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