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04 cooling guide

katzzero edited this page Jul 9, 2026 · 5 revisions

04 - Cooling Guide

The stock BC-250 heatsink is designed for passive rack cooling. Active cooling is mandatory for gaming.

Community cooling projects:

  • AMD clip system cooler adapter (biohazardv2.0 / bioizhere) — 3D-printable mount to attach standard AM4/AM5 clip-based coolers (air or AIO) to the BC-250. Tested with Zalman CNPS4X (92mm air). Printables
  • Case mods catalog — full list of community case designs in Case Mods & Custom Enclosures

Stock Heatsink - Know What You're Working With

  • Type: Passive aluminum fin stack
  • Fin orientation: Vertical, front-to-back
  • Mounting: Screwed directly to PCB (4 screws to remove)
  • Designed for: Rack-mounted servers with chassis airflow - not desktop use

Source: elektricM cooling.md (Stock Configuration, Active Cooling Required)

Three Heatsink Variants

Variant How to Identify Notes
9-row (most common) QR code next to PCIe 8-pin Standard version (elektricM cooling.md)
8-row No QR code Slightly fewer fins (elektricM cooling.md)
Thicker-fin variant Fewer, thicker-gauge aluminum fins Best stock cooling (elektricM cooling.md)

Quick ID from elektricM: QR code next to the PCIe 8-pin connector indicates the 9-row variant.

Source: elektricM cooling.md (Stock Configuration - Variants)

Heatsink Revisions

Some heatsinks have silkscreened markings showing where to place thermal pads; others do not. iamdarkyoshi (17 Mar 2026) reported owning two BC-250s where only the second unit had these pad-position markings.

CRITICAL: 4x Nylon Washers Under Heatsink Screws

The heatsink is secured by 4 spring-tensioned screws that pass through the back of the board. Under each screw head (on the VRAM/backplate side) there is a clear or black nylon washer that prevents the screw head from shorting PCB traces.

What goes wrong: During disassembly these washers often fall off and are lost. Reassembling without them creates a gap between heatsink and APU die, causing 90-100°C+ temperatures at idle.

Diagnosis: If the heatsink cannot be fully tightened (gap remains between die and heatsink), check whether the 4 nylon washers are present and correctly positioned. Shine a light through the side of the board to check for a visible gap.

Fix: Retrieve or replace the missing washers, realign them, and retorque. Users who found and re-installed missing washers reported temperatures "slowly decreasing" back to normal.

Sources: mzk10 (4 Dec 2025, 23 Jan 2026), .captainwasabi (23 Jan 2026). mzk10 summarizes: "In my day job it's always DNS. In bc250 chat it's always those damned washers."


Heatsink Modification

Method 1: Fin Straightening (Recommended)

The fins in the center are often bent from manufacturing or shipping. Opening them allows airflow through the heatsink.

Steps:

  1. Remove heatsink from board - always work off-board
  2. Use needle-nose pliers or flathead screwdriver
  3. Carefully push center fins apart
  4. Bend progressively - don't snap fins off
  5. Partial opening maintains structural integrity

Expected improvement: 5-10C

Source: elektricM cooling.md (Fin Straightening, Benefit: 5-10C temperature improvement)

Method 2: 3D Printed Scooper Tool

Method 3: Cutting (Advanced / Irreversible)

  • Dremel or hacksaw for larger openings
  • WARNING: Creates metal debris - dangerous near electronics
  • Router method possible but "the router bit will eat your heatsink for lunch" (snodrat, bc250-flex-chat, Jan 2026)
  • Fin removal is irreversible

Source: elektricM cooling.md (Fin Removal - High Risk Modification)


Fan Selection

Top Picks

Fan Static Pressure Speed (RPM) Airflow Noise Notes
Arctic P12 Pro 6.9 mmH2O 600-3000 77 CFM 39.7 dBA Community standard. Best price/performance. Only sold in multi-packs.
Arctic P12 Max 4.35 mmH2O 200-3300 81 CFM 0.6 Sone Higher max speed. Lower static pressure than P12 Pro.
Arctic P12 Pro PST CO 6.9 mmH2O 600-3000 77 CFM 39.7 dBA Dual ball bearing, cable sharing.
Noctua NF-F12 iPPC-3000 7.63 mmH2O 750-3000 110 CFM 43.5 dBA Premium industrial. Highest static pressure.
Noctua NF-A12x25 2.34 mmH2O Up to 2000 60.1 CFM 22.6 dBA Quietest premium option.
Arctic P14 PWM 2.40 mmH2O Up to 1700 72.8 CFM 38 dB(A) Larger 140mm - covers more heatsink area.
Wathai 120mm Blower 0.81-1.35 mmH2O Up to 3000 25-38 CFM 25-45 dB(A) Blower style. Not ideal for main cooling. (need confirmation - not in elektricM)
Arctic S12038-8K Server fan Up to 8000 Very high Very high "At 68% speed spanks a P12 Pro" (paul_lionking, May 2026)

Source notes on fan specs:

  • P12 Pro: Arctic official (arctic.de/en/P12-Pro). 3000 RPM / 77 CFM / 6.9 mmH2O. Noise: 39.7 dBA per Cybenetics independent test at max speed. Arctic marketing claims 25 dB(A) at low speed.
  • P12 Max: Arctic official spec sheet (arctic.de). Corrected from elektricM which listed 73.3 CFM / 6.9 mmH2O for both Pro and Max. Arctic's own data shows 81 CFM / 4.35 mmH2O for P12 Max.
  • P12 Pro PST CO: Arctic official (arctic.de/en/P12-Pro-PST-CO). Same fan performance, dual ball bearing.
  • NF-F12 iPPC-3000: Noctua official specs (noctua.at/en/nf-f12-industrialppc-3000-pwm/specification). Our file previously omitted these specs.
  • NF-A12x25: elektricM cooling.md
  • P14 PWM: elektricM cooling.md

IMPORTANT: Arctic P12 Pro Availability

The P12 Pro is NOT sold individually by Arctic. Available configurations:

  • 3-pack (A-RGB): Amazon ASIN B0DJD8MJ5S - confirmed
  • 5-pack (PST, non-RGB): Amazon ASIN B0DJDDCG4M - confirmed

Note: The 3-pack ASIN is the A-RGB version; the 5-pack is the PST (non-RGB, daisy-chain) version.

Sources: Arctic official site, Amazon listings

CPU Cooler Adapters (May 2026)

Community members are using standard CPU tower coolers with 3D-printed brackets:

Cooler Notes User
Thermalright Peerless Assassin 120 Best non-liquid cooler for the money. Requires 3D-printed bracket. Quiet, excellent cooling. Also available as $45 AIO version. dartzon, pepituwu, May 2026
Thermalright AIO Aqua Elite 240 V2, V4, V6 all confirmed working. V4 ASIN: B0DHZ5LSNP. V6: B0F98KYG6X (Amazon CA). gennro, sousapro, telefragger, May 2026
MSI AIO Used by FrenchHardware YouTube builds Community, May 2026
Bykski Custom Waterblock Possible future option for extreme AIO/water builds odinforrest, May 2026

dartzon (May 2026) used a Thermalright Peerless Assassin 120 with 3D-printed mounting bracket, coupled with a GPU backplate cooler with fans for VRAM chips. With 36 CU unlocked, Death Stranding 2 ran at ultrawide 1440p@60fps on high settings and temps never exceeded 72C.

Budget Options

  • Xbox One fan (3300 RPM) - creative repurposing (need confirmation - not in elektricM)
  • Thermalright TL-C12C - works but much lower static pressure than P12 Pro (need confirmation - not in elektricM)

Fan Mounting Methods

Method Pros Cons
Zip ties Simplest, no mods Can slip; less secure
Screws (factory holes) Most secure Requires drilling/cutting (elektricM warns NOT to drill heatsink)
Aluminum HVAC tape Seals air leaks, good contact Hard to remove (need confirmation - not in elektricM)
CPU cooler brackets Repurposed arms May not fit perfectly (need confirmation - not in elektricM)
3D printed shroud Best airflow, clean look Requires 3D printer

Primary methods (zip ties, 3D printed shroud, cardboard/foam shroud) are from elektricM cooling.md (Fan Mounting Options). Screws into heatsink: elektricM warns "Do not drill holes in the heatsink fins to screw fans directly."

Push vs. Pull Configuration

  • Single fan in center = best for most builds
  • Avoid two fans right next to each other (creates dead zone over APU core)
  • Push + pull (one each side) > push + push
  • 92mm fan on back helps with backplate VRAM cooling

(need confirmation - push/pull advice not directly in elektricM. 92mm fan advice from elektricM's secondary fan section)


Thermal Interface - What to Use Where

Location Recommended Thickness Notes
APU Die PTM7950 Phase Change Pad 0.2-0.25 mm Recommended in elektricM and prerequisites. 4-15C improvement claimed. ASIN B0F9Y5SCK2.
Front (VRAM/VRMs) Thermal pads 1.5 mm elektricM cooling.md + community consensus (vicomte.me, 12 Jan 2026)
Back (VRAM) Thermal pads 2.0 mm 8x GDDR6 chips. elektricM cooling.md + community consensus (vicomte.me, 12 Jan 2026). jayawesome (17 Mar 2026) confirmed having 0.5/1.0/1.5/2.0mm pads on hand and that they are stackable.

Source: elektricM cooling.md (Memory Thermal Pad Replacement: "1.5mm on front of board, 2.0mm on back"). Community corroboration: vicomte.me (12 Jan 2026) cited Snarks Domain "BC250 Thermal Putty Job" video with the same thickness recommendation. Note: prerequisites.md recommends "1mm or 1.5mm thickness" for backplate VRAM - discrepancy with cooling.md's 2.0mm back spec; the 2.0mm community consensus aligns with cooling.md.

PTM7950 Application Guide

  1. Clean APU die and heatsink copper with isopropyl alcohol
  2. Peel plastic from one side, apply to die
  3. Peel second plastic layer
  4. Torque heatsink screws evenly (cross pattern)
  5. First boot may show 80-90C - this is normal, it "cooks in" during initial thermal cycles

(need confirmation - application process not in elektricM. First boot behavior from community/Discord.)

Alternative: Thermal Putty

  • Fehonda LTP81 or similar
  • Self-squeezes to correct thickness - no measuring needed
  • Apply generously
  • "I stopped using thermal pads for everything. I use thermal putty." - community member (need confirmation - not in elektricM)

Thermal Paste Rankings (if not using PTM7950)

Paste Conductivity Notes
Thermal Grizzly Kryonaut 12.5 W/mK Best traditional paste. Recommended in elektricM (cooling.md + prerequisites). 3-5C drop vs MX-6.
Arctic MX-6 10.0 W/mK Current version. Recommended in elektricM (cooling.md).
Arctic MX-5 Discontinued Replaced by MX-6. pops1cl confirmed MX-5 is NOT better than MX-6.
Arctic MX-4 8.5 W/mK Good value. Recommended in elektricM (prerequisites.md + cooling.md).
Thermal Grizzly Duronaut ~12.5 W/mK Emphasizes long-term stability per Thermal Grizzly. Our file previously claimed 17.3 W/mK - reseller data shows ~12.5 W/mK. 15C drop claim unverified.

Source: elektricM cooling.md (Recommended Thermal Paste) lists MX-4, MX-6, Kryonaut, NT-H1, Thermalright TFX. Duronaut and conductivity values are NOT in elektricM - from community/Discord sources.


Temperature Reference

Safe Operating Temperatures (from elektricM cooling.md)

Component Idle Light Load Gaming Maximum
GPU/APU Edge 40-50C 50-60C 65-80C 90C
CPU (Tctl) 45-55C 55-65C 70-85C 95C
Memory (underside) 40-55C 50-65C 55-70C 80C

Source: elektricM cooling.md (Safe Operating Temperatures table)

Community Gaming Temperature Ranges (need confirmation - not in elektricM)

Range Assessment
60-65C Excellent (AIO or P12 Pro + PTM + opened fins)
65-75C Good (single 120mm fan, decent paste)
75-80C Acceptable (stock cooling)
85-90C Throttling zone
100-110C Critical - shutdown imminent

Stress Test Temperatures (Furmark) (need confirmation - not in elektricM)

Temp Assessment
80-85C Normal with good air cooling
90-96C High - check paste and airflow
108C Extreme OC without adequate cooling

Orientation Considerations (May 2026)

Board orientation affects cooling performance:

  • juliuuscaesar reported a 10°C difference between horizontal and vertical orientation
  • big_trov found only 1-2°C difference on his board, with power-plugs-down orientation slightly cooler
  • Test your specific board and mounting orientation for optimal thermals

With Liquid Cooling (240mm AIO)

Confirmed working models: Thermalright Aqua Elite 240 V2, V4, V6; MSI AIO series. Uses standard AM4 clip mounting with 3D-printed bracket (NexGen3D mount). (gennro, sousapro, telefragger, May 2026)

  • Gaming power draw: ~340W (Furmark + CPU stress)
  • GPU stable up to 4.1 GHz CPU / 2300 MHz GPU
  • AM4 clip-style AIOs with printed adapters are the standard approach

Multi-Fan Control (J4003 Header)

The NCT6686D chip supports 4 additional fan control circuits via the J4003 header on the board. These can be controlled by software such as CoolerControl (essdee4336, May 2026). Reference pinout: mothenjoyer69/bc250-documentation.


Recommended Setup (TL;DR)

  1. Open heatsink fins in center (scooper tool or fin bending)
  2. PTM7950 phase change pad on APU die
  3. 1.5mm pads on front, 2.0mm on back (or thermal putty)
  4. Arctic P12 Pro zip-tied or mounted over opened section
  5. Optional: 92mm fan on backplate for VRAM cooling
  6. Fan curve: 30% at 40C - 50% at 60C - 75% at 70C - 100% at 80C

(need confirmation - recommended setup not in elektricM as a numbered list)


3D-Printed Fan Shrouds & Accessories

Design Link Notes
ViRazY Fan Shroud (140mm + 120mm) https://www.printables.com/model/1339540 Intake + exhaust combo (need confirmation - URL returned transport error)
Cooling Solution https://www.printables.com/model/1385007 Full cooling solution (need confirmation - URL returned transport error)
140mm Fan Mod (4U12G case) https://www.printables.com/model/1674470 For Asrock 4U12G case (need confirmation - URL returned transport error)
BC-250 Scooper (fin tool) https://www.printables.com/model/1282906 Essential for fin work (need confirmation - URL returned transport error)
BC-250 Shell Case https://www.printables.com/model/1228207 Simple enclosure (need confirmation - URL returned transport error)
Minimal Case + Flex PSU https://www.printables.com/model/1423572 Compact Flex ATX build (need confirmation - URL returned transport error)
BC-250 Case (ATX PSU) https://www.printables.com/model/1553599 For standard ATX PSUs (need confirmation - URL returned transport error)
BC-250 Sleeve Adapter https://github.com/onemorecap/bc-250-sleeve-adapter 120mm fan adapter. Listed in elektricM cooling.md
BC-250 Custom Case https://github.com/isaacalvex/BC-250-Custom-Case Alternative enclosure. Listed in elektricM cooling.md

GitHub URLs verified present in elektricM cooling.md (Popular Designs section).

Other Printables models: not verified - all returned transport errors during audit.


VRAM Cooling - Don't Forget the Back!

The GDDR6 memory chips sit on the back of the board and have no temperature sensor. Overheating causes:

  • Pixel artifacts during gaming
  • System crashes after 30-60 minutes
  • Instability at high settings

Source: elektricM cooling.md (Backplate VRAM Cooling Solutions, Memory Thermal Pad Replacement)

Solutions:

  1. Apply 2mm thermal pads to backplate VRAM chips (elektricM cooling.md: "Apply 2mm thermal pads directly on backplate VRAM chips")
  2. Ensure case has positive airflow over backplate (elektricM cooling.md: Rear Case Airflow)
  3. Mount a small fan (80mm) blowing directly on backplate (elektricM cooling.md: Secondary Fan 80mm)
  4. Attach aluminum heatsink plate to back of board (elektricM cooling.md: "Attach aluminum heatsink or plate if available")

Heatsink-to-PCB Thermal Pads

iamdarkyoshi (17 Mar 2026) tested adding thermal pads between the heatsink and PCB directly behind individual GDDR6 memory ICs. The left-side ICs (with pads installed) were visibly cooler than the right-side ones (stock, without pads). This helps conduct heat from the memory chips through the PCB and into the heatsink.

How to do it: Reuse extra pad material from the backplate pads, squish it slightly to make it thick enough to contact both surfaces. The target thickness is "just barely thicker than the thermal pads used on the back." iamdarkyoshi recommends scrunching the stock backplate pad material to make it narrower and slightly thicker.

Note: Not all heatsinks have markings for these additional pad positions. iamdarkyoshi's second board had silkscreened marker positions; the first did not.

Key takeaway: Front cooling alone isn't enough. Pay attention to the back.

Sources: elektricM cooling.md (Backplate VRAM Cooling Solutions), iamdarkyoshi (17 Mar 2026)

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