TDP vs. PPT: Why 400W Is Not a Simple Number

To find a “400W” motherboard, we must first understand the metric. CPU manufacturers use different terms for power consumption.

• Intel (TDP vs. MTP): For Intel workstation chips, the TDP (Processor Base Power) is the nominal rating. The Maximum Turbo Power (MTP) is the peak sustained draw. On the Xeon w9-3595X, the 385W TDP is very close to its actual MTP.
• AMD (TDP vs. PPT): AMD’s Threadripper CPUs have a nominal 350W TDP. The true limit is the Package Power Tracking (PPT), which can be set much higher. A 350W TDP AMD CPU can draw nearly 800W under high load.

This means an Intel 385W platform is built for a 385W limit. An AMD 350W platform is built to exceed 400W, sometimes by a large margin. We must include both in our search.

The Decisive Factor: The Voltage Regulator Module (VRM)

The motherboard’s VRM is the component that handles the 400W+ load. It converts 12V power from the PSU into the low voltage (e.g., 1.2V) and high current (amperage) the CPU needs.

A 400W load at 1.2V requires the VRM to deliver **333 Amps** of current. The VRM spreads this load across “phases”. More phases mean less work and less heat per component.

Interactive: VRM Load Distribution

Visualizing a 333 Amp load. More phases spread the load, reducing heat and improving stability.

VRM Component Deep Dive

A VRM “phase” is not just one component. It’s a team of components working together. The quality of these parts is as important as the phase count.

• 1. MOSFETs

  These are the switches that control power flow. High-end boards use “DrMOS” (Driver-MOSFET) chips that are more efficient and generate less heat than older designs.

• 2. Chokes (Inductors)

  These boxed coils stabilize the current. You want chokes rated for high amperage (e.g., 90A or 105A) that do not “whine” under high load.

• 3. Capacitors

  These components smooth out the final voltage. Look for “10K” or “12K” Japanese solid-state capacitors, rated for long life at high temperatures.

The VRM Heatsink Fan

Liquid coolers (AIOs) are popular for these CPUs. They cool the CPU well but create a new problem: no incidental airflow over the VRM. The VRM can then overheat and throttle the system. To solve this, manufacturers now add small, dedicated fans directly to the VRM heatsinks.

A simple finned-aluminum monoblock is good, but a stacked-fin heatsink (like on a CPU cooler) is better. The presence of these fans and advanced heatsinks is a clear sign a board is built for 400W+ loads.

Platform 1: Intel W790 (LGA 4677)

The W790 chipset is Intel’s workstation platform. Its features depend on the CPU you install. The “Expert” (Xeon W-3500/W-3400) CPUs unlock 8-channel DDR5 memory and 112 PCIe 5.0 lanes. The “Mainstream” (Xeon W-2500/W-2400) CPUs are limited to 4-channel memory and 64 lanes.

W790 Motherboard Comparison

Platform 2: AMD sTR5 (WRX90 & TRX50)

The sTR5 socket supports all Threadripper 7000 and 9005 series CPUs. It is split into two chipsets:

• AMD WRX90: The full workstation platform. It unlocks 8-channel DDR5 memory and 128+ PCIe lanes. It is *only* compatible with Threadripper PRO WX-Series CPUs.
• AMD TRX50: The HEDT platform. It is limited to 4-channel DDR5 memory and 80+ PCIe lanes. It supports *both* the HEDT (non-Pro) and PRO WX-Series CPUs.

All sTR5 motherboards are engineered to handle loads well over 400W. The ASUS WRX90E-SAGE, for example, has a massive 32-phase VRM. This is not for the 350W TDP. It is for the 800W+ loads that overclocking can produce.

AMD sTR5 Motherboard Comparison

Platform 3: AMD SP5 (Server)

The most literal answer is the server market. The AMD SP5 socket supports EPYC 9004 and 9005 series CPUs, which include models with an explicit 400W TDP. Motherboards like the **T2SEEP** are advertised to support these 400W CPUs.

This is almost certainly the wrong choice for a workstation. Server platforms prioritize core count and 12-channel memory bandwidth over high single-core boost clocks and overclocking support.

Interactive Platform Selection Guide

Use this simple flowchart to determine which platform best suits your needs. The primary difference comes down to workload, I/O requirements (like multi-GPU setups), and memory bandwidth.

Technical Deep Dive: PCIe Lane Allocation

A key differentiator for workstation platforms is the number of available PCIe lanes. These lanes are the data highways between your CPU and components like GPUs and storage. For AI and machine learning, running multiple GPUs (e.g., four NVIDIA RTX 6000 Ada) requires a massive number of lanes.

A consumer platform might offer 16 or 20 lanes in total. These workstation platforms offer far more, but they are not all equal.

System-Wide Demands: Power, Cooling, and Cost

A 400W CPU does not exist in isolation. It is the heart of a system that can easily pull over 1000W from the wall. This has critical consequences for your power supply and CPU cooler, which must be chosen carefully.

Power Supply (PSU) Requirements

A standard 750W PSU is not sufficient. For this class of hardware, a 1200W PSU should be considered the minimum.

• Multiple EPS Connectors: These motherboards require two, and sometimes three, 8-pin EPS CPU power connectors. Most consumer PSUs only have one. You must select a high-wattage (1200W, 1500W, 1600W) unit that provides the necessary CPU power cables.
• Transient Spikes: The 400W rating is a sustained load. The CPU and paired GPUs can create brief power spikes (transients) that are much higher. A quality, high-output PSU (ideally ATX 3.0 compatible) is required to handle these spikes without shutting down.
• GPU Power: A 400W CPU is often paired with one or more 350W+ GPUs. A system with a 400W CPU and two high-end GPUs can easily approach 1300W under load (400W CPU + 700W GPUs + 200W for motherboard, RAM, etc.). A 1600W PSU is a safe and necessary choice for such a build.

CPU Cooler Compatibility

The LGA 4677 (Intel) and sTR5 (AMD) sockets are physically massive. A cooler from a consumer AM5 or LGA 1700 build will not fit.

• Mandatory HEDT Bracket: You must purchase a CPU cooler that *explicitly* includes the correct mounting bracket for sTR5/SP5 or LGA 4677. These are rarely sold separately and do not come with standard coolers.
• Full-Cover Cold Plates: The CPU’s integrated heat spreader (IHS) is too large for most coolers. You need a cooler with an oversized cold plate designed to cover the entire IHS. Coolers like the Noctua NH-U14S TR5/SP5 or specific 360mm/420mm AIOs from Asetek are designed for this. Using a cooler with a smaller, standard cold plate will result in overheating.

Physical Realities: Form Factor and Case

These motherboards are physically enormous. They will not fit in a standard ATX mid-tower case. You must plan your case purchase around the motherboard’s form factor, which is typically E-ATX, CEB, or EEB.

Understanding Workstation Form Factors

Here is a quick comparison. The main issue is not just the height and width, but the different standoff mounting hole locations.

Example Build Templates

Your choice depends on your workload. All platforms listed here handle 400W+. The real differences are I/O, memory channels, and price.

Frequently Asked Questions