No, VRMs are not required for RAM on DDR5 motherboards.
No, VRMs are not required for RAM on DDR5 motherboards.
I've learned that DDR5 chips often have built-in voltage regulators to achieve faster performance. This suggests that most motherboards should include VRMs for RAM, unlike earlier models such as DDR4 and below. For instance, an 8+2 configuration means eight phases for the CPU and two for RAM. It doesn't appear to be uncommon. It might still make sense for VRMs to be present on RAM modules, even if not strictly required. Additionally, some high-end boards use three types of VRMs: two 10+2 and another 2+2 configuration. What does this look like in practice? It seems unrelated to the specifics of DDR5.
It seems focused on optimizing power use and scalability in data centers. Large buffered DIMMs consume significant energy, so placing the PMIC close to the chips reduces unnecessary power draw from the motherboard. The "+2" value actually indicates an additional voltage rail—on LGA 1700 it’s VCCIN, feeding the CPU memory controller, PLL components, and related voltages. On AMD systems, "+2" relates to the SOC voltage that supplies the memory controller, iGPU, and input/output operations. Memory power consumption, especially for DDR4, was seldom highlighted outside server environments. The exact meaning varies by platform; often it points to iGPU power, though this isn't always certain. For LGA 1151, the sequence includes VCore, VCCSA, VCCIO, and IGPU. On AM5, the third listed stage typically corresponds to VDD_MISC, akin to VCCIN on LGA 1700. Updated April 24, 2023 by RONOTHAN##
The ATX power supply only provides 3.3V, 5V and 12V. The DDR5 modules require around 1.5V or similar, so a VRM is necessary to change 5V to those lower levels. The DC-DC converter built into the DDR5 module then adjusts this low voltage down to about 1V or slightly higher. A single conversion might suffice, but multiple stages could be needed depending on chip requirements.
According to what I understand, DDR5 supports input voltages of either 5V or 12V, not 1.5V. This is important because the PMIC handles Vpp which, according to JEDEC standards, operates at 1.8V—higher than the 1.5V supply. While a 12V to 5V converter is often present on the board, it’s mainly due to the higher capacity of the 12V lines compared to the 5V lines from the power supply.
It seems there was a misunderstanding about the voltage range. While 12V is the nominal value, some PMIC chips operate effectively from as low as 4.5V. I found an example here: https://www.ti.com/product/TPS53832#features The DC-DC converter provides 1.1V and 1.8V for the RAM chips. Thanks for the update.