AMD Ryzen 9000 · AM5 / Single-tower air cooler
Does the Thermalright Assassin King 120 SE fit the Ryzen 7 9800X3D?
Yes. The Thermalright Assassin King 120 SE fits the Ryzen 7 9800X3D with 68 W of thermal headroom; we estimate 77 °C under sustained load and 51 °C while gaming, an excellent match.
Reviewed by Farrukh Sufyan SarwarHow we estimate temperaturesPublished Prices verified Model v1.2 · data updated
Full load
77°
Gaming
51°
Idle
32°
Excellent fit
Safe at 77 °C full load
18 °C below the 95 °C junction limit under a sustained all-core load.
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The Thermalright Assassin King 120 SE is an excellent match for the Ryzen 7 9800X3D, with 68 W of headroom above its 162 W boost ceiling. We estimate 51 °C in games and 77 °C under a full all-core render, leaving quiet-fan-curve room.
Thermal estimate
Both figures assume a 35 °C case-internal ambient and the cooler's sustained rating; the CPU's own junction limit caps the full-load figure.
| Load | Estimate |
|---|---|
| Idle | 32 °C |
| Gaming | 51 °C |
| Full load | 77 °C |
| Junction limit | 95 °C |
- 0–85 % comfortable
- 85–100 % fans ramp
- 100 %+ throttles
- Thermal headroom
- +68 W
- CPU boost / gaming draw
- 162 W / 80 W
- Cooler sustained rating
- 230 W
- Junction limit
- 95 °C
- Cooler height
- 160 mm
- RAM clearance
- Unrestricted
- Sockets in the box
- AM4 · AM5 · LGA1200 · LGA1700 · LGA1851
What the numbers mean for this build
- 01
68 W of sustained headroom
The Ryzen 7 9800X3D uses 70 % of the Thermalright Assassin King 120 SE's rated capacity at its 162 W ceiling, which means the fans can run a relaxed curve and stay quiet even in Cinebench.
- 02
AM5 hotspot offset
Ryzen 9000 dies sit toward the south edge of the thick AM5 heat spreader. An offset mounting bracket for the Thermalright Assassin King 120 SE (Thermalright, Noctua and others sell them for a few dollars) shifts the cold plate 7 mm and typically drops load temperatures 2 to 4 °C. The Ryzen 7 9800X3D's junction limit is 95 °C, so every degree counts.
- 03
Chassis height alert: 160 mm cooler
At 160 mm the Thermalright Assassin King 120 SE exceeds the 160 mm limit of many compact Micro-ATX and tempered-glass mid-towers. Confirm the case's maximum CPU cooler height is at least 163 mm before ordering.
Will it physically fit?
Drag the sliders to your memory height and case limits. The schematic moves with you and shows where the Assassin King 120 SE clashes.
This heatsink does not overhang the DIMM slots.
Listed as “CPU cooler clearance” in the case spec sheet. This cooler is 160 mm tall.
- RAM heightFits
The heatsink does not overhang the DIMM slots, so any RAM height fits.
- Cooler height vs caseFits (+5 mm)
5 mm between the cooler and the side panel.
Overall Fits for the Assassin King 120 SE with your inputs.
Schematic, not to product scale.
Buy it, or compare the alternatives
Three tiers picked for this exact CPU: the cheapest tower that passes, the quietest liquid option per dollar, and the best low-profile heatsink.
This pairing
$17.29as of Nov 2, 05:59 AM UTC · In Stock
(opens Amazon in a new tab)ThermalrightAssassin King 120 SE
Single-tower air cooler · 160 mm
230 W rated, 68 W headroom on the Ryzen 7 9800X3D.
Top air value
$29.99as of Nov 2, 05:59 AM UTC · In Stock
(opens Amazon in a new tab)ID-CoolingFROZN A620 Pro SE
Dual-tower air cooler · 157 mm
98 W of headroom; the best-value tower air cooler that passes on this CPU
Silent liquid pick
~$54
(opens Amazon in a new tab)ThermalrightFrozen Infinity 360
360 mm AIO liquid cooler · 52 mm
Estimated 64 °C under full load with quiet fan curves
Small-form-factor pick
$27.99as of Nov 2, 05:59 AM UTC · In Stock
ThermalrightAXP120-X67
Low-profile air cooler · 67 mm
67 mm tall; best low-profile option, but expect throttling in all-core loads
Not recommended for this CPU
Full analysisProduct prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply to the purchase of this product.
Related reports
Other coolers on the Ryzen 7 9800X3D
- Thermalright Peerless Assassin 120 SEExcellent fit
- Thermalright Peerless Assassin 120Excellent fit
- Thermalright Phantom Spirit 120 SEExcellent fit
- Thermalright Phantom Spirit 120 EVOExcellent fit
- Noctua NH-D15Excellent fit
- Noctua NH-D15 G2Excellent fit
- Noctua NH-D15SExcellent fit
- Noctua NH-D12LExcellent fit
- be quiet! Dark Rock Pro 5Excellent fit
- Scythe Fuma 3Excellent fit
Thermalright Assassin King 120 SE on other CPUs
Terms used on this page
- Thermal 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.
- TjMax
- The maximum junction temperature the maker allows, typically 95–100 °C. AMD lists 90 °C for the Ryzen 7 5800X3D, 89 °C for the 7800X3D and 95 °C for the 9800X3D. At TjMax the CPU throttles clocks to stay in place; it will not overheat, but it will lose performance.
- PPT
- 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.
- Thermal 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.
- RAM 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.
- CPU 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.
- AM5 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.
Frequently asked questions
Will the Thermalright Assassin King 120 SE keep the Ryzen 7 9800X3D from thermal throttling?
Yes. The estimated full-load temperature is 77 °C, 18 °C below the 95 °C throttle point.
What temperature should I expect while gaming on the Ryzen 7 9800X3D with this cooler?
Around 51 °C with a 35 °C case ambient, because GPU-bound games only draw about 80 W from the CPU package. Cooler rooms and better case airflow lower that figure.
Does the Thermalright Assassin King 120 SE fit tall RGB RAM?
Yes. The heatsink does not overhang the memory slots, so any module height works.
Is the Thermalright Assassin King 120 SE compatible with the AM5 socket?
Yes, AM5 hardware is included. Supported sockets: AM4, AM5, LGA1200, LGA1700, LGA1851.
Hubs: Ryzen 7 9800X3D · Thermalright Assassin King 120 SE · AM5