Thermal glossary

01PL1 / PL2

Intel's two power limits. PL1 (Processor Base Power) is the sustained draw the CPU settles at; PL2 (Maximum Turbo Power) is the short-term boost ceiling. Many desktop boards run PL2 indefinitely, so a cooler must be sized for PL2, not PL1.

Also: PL2 · PL1 · Processor Base Power

02PPT

Package Power Tracking, AMD's socket power ceiling. It is roughly 1.35 × TDP (65 W TDP → 88 W PPT, 105 W → 142 W, 170 W → 230 W) and is the figure a Ryzen cooler actually has to dissipate.

Also: Package Power Tracking · PPT limit

03TDP

Thermal Design Power, the manufacturer's nominal sustained heat output. Modern CPUs exceed it under boost, which is why this site rates coolers against PL2 or PPT rather than TDP.

Also: thermal design power · base TDP

04TjMax

The maximum junction temperature (typically 95–100 °C, 89 °C on Ryzen X3D parts). At TjMax the CPU throttles clocks to stay in place; it will not overheat, but it will lose performance.

Also: junction limit · junction temperature · Tj Max

05Thermal throttling

Automatic clock reduction when the CPU hits TjMax. A pairing is flagged as a throttling risk when the modelled full-load temperature reaches the junction limit or the cooler is rated 15 W or more below the CPU's boost power.

Also: throttling · throttle

06Thermal headroom

The cooler's sustained dissipation rating minus the CPU's boost power limit, in watts. Positive headroom lets fans run slower and quieter; 25 W or more is rated Excellent here.

Also: headroom

07RAM clearance

The tallest memory module that fits under an air cooler's front fan in its stock position. Dual-tower coolers with less than 42 mm clash with tall RGB kits (typically 44 mm) unless the fan is raised.

Also: memory clearance · DIMM clearance

08CPU cooler height

The installed height of an air cooler from the motherboard, compared against the case's published CPU cooler clearance. Coolers at or above 160 mm exclude many compact Micro-ATX and tempered-glass mid-towers.

Also: cooler clearance · case clearance · maximum CPU cooler height

09AIO liquid cooler

A sealed closed-loop liquid cooler with a pump block and a 120–420 mm radiator. Radiator length determines case compatibility; thickness plus fans determines top-mount clearance above the VRM heatsinks.

Also: AIO · all-in-one liquid cooler

10Dual-tower air cooler

An air cooler with two fin stacks and a fan between them (often a second in front). Highest air-cooling capacity, but the front fan overhangs the DIMM slots, which is where RAM clearance limits come from.

Also: dual tower · twin tower

11AM5 offset mount

A mounting bracket that shifts the cooler's cold plate a few millimetres toward the AM5 die location, which sits south of centre under the thick heat spreader. Typically lowers Ryzen 7000/9000 load temperatures by 2–4 °C.

Also: offset bracket · hotspot offset · contact frame

12ILM

Intel's Independent Loading Mechanism, the socket clamp. On LGA1700 the stock ILM bends the long CPU package slightly, reducing cold-plate contact; contact frames replace it to improve temperatures.

Also: independent loading mechanism · socket ILM

13Sustained dissipation rating

The continuous heat load, in watts, a cooler can remove at acceptable noise. This site uses realistic sustained figures rather than marketing peak numbers, and models temperature as ambient plus load ÷ rating × a per-load scale.

Also: rated dissipation · cooler rating · rated capacity

See the constants and formula behind these terms on the methodology page.