Archive: CPUs Ranked by Noise / Heat

Update March 6, 2004 A year's worth of updates; new entries in blue boxes.
Update March 7, 2003 Added info on recent AMD and Intel CPUs, and the VIA Eden M series boards. Also made changes to the text under "Some Fundamentals".
Update Aug 26, 2002
First published July 21, 2002 by Mike Chin

NOTE: Consider this article an archive; not updated since March 2004. It may be interesting to read, but doesn't cover the umpteen new models that have appeared since. Check for more recent articles in the CPU & motherboards section.

The central processing unit is the most significant source of heat in a modern PC. The most powerful of current desktop CPUsgenerate over 100W of heat which must be removed from the processor core and out of the PC case. The standard air-cooling method is by conduction from the CPU to a heatsink, then by convection into the air within the case, and finally evacuation of the hot air via PSU and/or case fans. In the case of water cooling, the first step is by conduction to pump-circulated water via waterblock, conduction from the water to a cooling radiator often placed outside the case, then finally convection into the outside air from the radiator via forced airflow from a fan.

Given the high thermal densities (high heat generated in small area / volume) of today's fastest CPUs, cooling them without fans is virtually impossible without resorting to custom fabrication of massive, efficient conduction/convection devices. Cooling them quietly is definitely feasible, however. If judicious undervolting and underclocking are utilized in conjunction with efficient heatsinks and optimized case airflow, it is possible to approach state-of-the-art-performance with very little noise.

The list below a ranking of processors by how easy they are to run quietly.

Some Fundamentals:

  • Although fanless CPU cooling is a kind of Holy Grail for many enthusiasts, it is, by itself, not enough to make a computer silent. Removable of the hot air around the CPU and its heatsink becomes a challenge. For true silent operation, the noise of a hard drive must also be tamed, and the heat from a PSU removed from the case without a fan. These are complex technical challenges that can be very expensive to tackle.
  • The difference between silent and virtually inaudible is very small in subjective terms, but very large in terms of cost and difficulty of implementation. Total silence is much harder to achieve. By virtually silent, we mean inaudible in most acoustic environments from more than 2~3 feet away. For most computer users, such a noise level is indistinguishable from silence. For under desk placement <20 dBA/1 meter can be generally regarded as virtually inaudible; for on-desk placement, it's probably more demanding, perhaps <16 dBA/1m. These numbers really depend on background noise and user sensitivities.
  • We generally recommend virtually inaudible as a viable, practical alternative to complete silence.
  • It is not practical to seek cutting-edge performance in a quiet or silent PC, but it is possible to get close. It is technically challenging, and considerably more expensive to achieve quiet with a hotter CPU; the necessary cutting edge cooling technology always costs more. A broad rule of thumb:
  • You can build a virtually inaudible system with a CPU rated at ~90% of the fastest version by using the best aircooled HS on SPCR's recommend list and a quiet fan running at reduced voltage. For example, if the fastest XP is rated at 3000+, a model rated at ~2700+ can probably be adequately cooled with a Thermalright SLK900 and a Panaflo 80mm "L" fan at ~7V in a case that is optimized for excellent airflow. This can give you virtually inaudible performance.

    Development of heatsink performance occurs in direct response to CPU speed/heat. The highest performance HSF can safely cool the fastest, hottest CPU at any given time -- but at the expense of high airflow fans that make a lot of noise. Back off on the fan speed, and you generally find that while it is not enough to cool the fastest CPU, it is OK with a CPU that is a bit slower and cooler. This is not exactly scientific but it is based on several years of watching the dance between CPU and HSF makers.

  • Aside from considerations of relative value for money, artificial benchmark testing and geek one-upmanship, we place little value on CPU performance differences smaller than ~25%. In terms of the real computing experience, smaller differences are generally not relevant and subject to so many other influences such as RAM, hard drive performance, video card performance and so on.

Many models no longer in production are among the CPUs in our list. The fact is that many of these are widely available on the used market, and sometimes as old stock from retailers. Many are in systems used by readers who are satisfied with the performance of these older systems and would simply like to make them quieter.

Note that only processors that can be used in desktop motherboards are covered, including some mobile processors. Server-specific processors are excluded, at least for the time being.

We make no attempt to rank the processors by computing power. That is already done by a hundred other web sites. In general, for office & web type apps, almost anything faster than a Celeron 300A seems adequate. As soon as games, electronic publishing or serious multimedia is involved, then the minimum CPU requirement is doubled, tripled or quadrupled. A fast video card can help and a slow one can hinder.

Guide to the List

Make / Model: Manufacturer and model number

Cool: Our assessment of how easy or difficult it is to cool the CPU, which is directly related to how quietly it can be run. It is based on heat dissipation (Watts) and on how easily the parameters of CPU bus speed, core voltage, and multiplier can be manipulated to lower its heat dissipation. Other factors such as the allowable maximum size/weight of the heatsink, the contact area between the CPU core and heatsink, and the range of CPU-specific features found on motherboards for the processor are also taken into account. Ranked from 1-10 with 10 being perfectly easy to cool without noise, and 1 being very difficult.

NOTE! Low cool ranking does NOT mean that a processor cannot be run silently. It just means that it is more difficult to do than with a CPU ranked higher. As the ranking approaches 1, progressively more sophisticated, extreme methods, effort, and/or money is required to achieve silent cooling.

The wattage information comes directly from manufacturers' web sites and from the incredibly useful, constantly up-to-date compilation, Processor Electrical Specifications by Chris Hare. Unless noted otherwise, wattage references are to typical power dissipation, not maximum or peak.

Detailed information about AMD processor, some of which simply can't be found at AMD's web site, is available here:

Comments: The cool rating is incomplete without the comments. Each comment is dated by month and year at the end of the entry. References to Q ratings refer to Recommended Heatsinks.

Prices are not provided as they are subject to great market fluctuations.

* * *

NOTE on Integrated Heat Spreaders: The primary purpose of an integrated heat spreader (IHS) is to reduce localized hot spots on the die, and increase user friendliness by creating a package that is less susceptible to mechanical damage or thermal damage from sloppy installation.

Intel marketing material seems to suggest that an IHS helps to better cool the processor. Intel technical material suggests that the opposite is true, that an IHS can actually double the overall thermal resistance. Check out the following Intel document for discussion about how the IHS makes cooling a CPU more difficult during burn-in testing. Just search for "IHS" in this document to skip to the relevant parts:

* * *

Make / Model
VIA C-3 (700MHz - 1.2GHz)
The natural choice for a silent PC, even the fastest C-3 variants dissipate no more than ~10W, cooled easily by a modest heatsink without fan. Robust and resistant to thermal damage as shown by VIA's Beat the Heat video. For business and general home applications, performance is on par with similarly clocked offerings from AMD and Intel. Relatively poor FPU performance can be compensated in part by a powerful video card for gaming and imaging applications. 20/7/02
VIA Eden platform

Not a CPU per se, but an embedded-CPU plus motherboard package, the original VIA Eden Mini-ITX integrated motherboards utilize C3 variants currently running at 533~1000 MHz. Extremely small with vanishingly low power consumption, some of these integrated platforms are designed to be run fanless for a variety of applications. The VIA EPIA-5000 and the newer EPIA M6000, which has superior multimedia performance, both run fanless. The 800, M9000 and M10000 all feature a ~25 dBA/1M fan. See EPIA board reviews in the Prebuilt / SFF PC section. Mar 8/03

Intel Celeron Coppermine (533-600 MHz) 1.5Vcore
These low voltage models feature low power (11-13W) and are good candidates for fanless cooling. Adequate performance. 20/7/02
AMD K6-II/III (233-550MHz)


Typical wattage of these AMDs range from 8W to 18W. The former is suitable for near-fanless operation; the latter for very quiet operation. Performance is not quite up to Intel equivalent clock P2 & P3; they're pretty slow by today's standards. 20/7/02
Intel Pentium-M Centrino (900 MHz - 1.7 GHz)
Intel remains mum on desktop deployment of this powerful CPU. Supported for desktop only by a tiny number of very expensive limited edition industrial Mini-ITX and Micro-ATX boards, the P-M matches the performance of P4s of double the clock speed. 1.3V P-M at 1.3-1.7GHz are 26-30W; the 1.2V P-M 1.2GHz is just 20.8W. Lower speed/voltage version down to 900MHz drops below 10W, with fanless cooling easily possible; Speed Step technology tends to further lower real power. Far different from P4-Mobile, which has power inefficiency similar to desktop P4. March/04

Intel P4(A) Northwood (1.6-2.0 GHz)

P4 with 512K L2 cache, 1.5V core voltage, and 0.13µ core has improved power efficiency. Typical power ratings of 38W to 52W, sub-2GHz models can be run quietly with stock HS and quiet 80mm fan at low voltage, due to built-in thermal management and large HS form factor. Excellent thermal protection hurts performance when pushed hard, but makes P4s virtually impossible to burn. Good candidates for use in quiet low-airflow systems. 20/7/02
Intel Celeron (233-333 MHz)
In both SEC and PGA casing, these low wattage (16-20W) processors are easy to cool quietly. Obviously slow. 20/7/02
Intel Celeron Coppermine (533-800 MHz) 1.7Vcore
Standard voltage models with 14~20W power; should be easy to cool quietly. Decent performance still. 20/7/02
Intel PIII Coppermine (500~750 MHz)
Low power dissipation (13-19W) makes the P3s at these clock speeds suitable for fanless cooling when combined with heatsinks rated at Q8 or better, a little undervolting, and decent case airflow. Performance good enough for lots of current apps. 20/7/02
Intel PII Deschutes (266-450 MHz)
With power dissipation of 17-28W, these Slot 1 CPUs can be easily run with a quiet fan at reduced voltage when combined with a good heatsink. Long in the tooth, performance-wise. 20/7/02
AMD Duron (Spitfire core 550~750 MHz)
19~30W. Less heat than K7 or K75 but small die area. Easy to unlock multiplier, good performance. 1/08/02
Intel Celeron Coppermine (800MHz - 1.1GHz)
24-33W. A Q 7 or 8 ranked HS plus low noise 80mm should cool these quietly. 20/7/02
AMD Athlon K75 (550-750 MHz)
2nd generation 0.18µ Slot-A Athlons are more efficient than earlier K7. These models are rated for 28-35W typical; should be fine with large heatsink and quiet fan. Faster than similarly clocked P3s. 20/7/02
AMD Duron (Spitfire core 800-950MHz)
33~42W. Less heat than K7 or K75 but small die area. Easy to unlock multiplier, great performance/price. 1/08/02
AMD Athlon Thunderbird (750MHz - 1.0GHz)
Rated for 36-49W typical, more efficient than K75s. Socket-A. Pencil trick to unlock multiplier eases underclocking without much loss of performance by increasing bus speed. Adequately cooled with 5V quiet 80mm fan and Q8 ranked HS. 20/7/02
Intel Celeron Mendocino (366-533 MHz)
20-28W typical power dissipation; respond well to a decent HS and quiet larger fan. 20/7/02
Intel PIII Coppermine (700~933 MHz)
Cooling requirements of these 18-31W Coppermines is modest, performance quite adequate still. 20/7/02
Intel Celeron Tualatin (900MHz - 1.4GHz)
0.13µ core, 26-35W power dissipation is similar to 800MHz-1.1GHz Coppermine Celerons, but equipped with a heat spreader like the P3 Tualatin. 256K L2 cache for better performance. Tualatin support motherboard needed. 20/7/02

Intel PIII / S (Tualatin) (1.0-1.4 GHz MHz)

The 0.13µ P3s (both 256K and S 512K cache versions) feature an integrated heat spreader that may make them harder to cool than the typical power ratings (28-34W) suggest. Requires Tualatin supported motherboard. 20/7/02
Athlon XP Mobile 2500+ (Barton core)
According to this unofficial page, the 1.45V XP-M is 45W all the way to 1867 MHz core speed. Discussions on SPCR Forums and other websites. Mar/04
AMD Duron (Morgan core 900MHz -1.3 GHz)
43~60W. Easy to unlock multiplier, great performance/price. Mar 07/02
AMD Duron (Applebred core 1.4-1.8 GHz)
57W. Mar/04
AMD Athlon K7 (500-700 MHz)
In Slot-A form factor, the early Athlons (38-45W) can be run with large heatsinks and quiet fans. 20/7/02
AMD Athlon K75 (800MHz - 1.0GHz)
The faster 0.18µ Slot-A Athlons range in typical power from 43-60W, considerably hotter than slower models. 20/7/02
AMD Athlon Thunderbird (1.1 - 1.4 GHz)
54-65W typical power. Pencil unlock of clock multiplier and undervolting can allow for quiet cooling of faster models in range. Requires at Q8 ranked HS. 20/7/02
AMD XP/MP Thoroughbred 1700+ to 1900+ (1.46 - 1.6 GHz)
Advantage of 0.13µ core offset by smaller heat transfer contact area and higher clock speeds. 45-48W typical power. 20/7/02

Intel PIII Katmai (450-600 MHz)

25-35W power dissipation puts these models in between Deschutes & Klamatth core P2s. 20/7/02
Intel P4 (A, B, C, G) Northwood (2.2-2.53 GHz)
The >2.2Ghz P4 NW with typical power ratings of 55-62W are not easy to run quietly, but OK with undervolting, large powerful heatsink and quiet fan. 20/7/02
AMD XP Barton 2500+, 2800+ (1.83-2.08GHz)
68W max. No significant change from T-bred "B" with the same "effective clock speed rating", but the die area is 25% larger so should mean more effective transfer of heat to the HS and thus lower temps for the same level of computing power. Mar 7/03
Athlon 64 754, 939 socket (2800+ to 3800+)
3 - 5
Max 89W power rating seems to apply to fastest model & is mitigated by Cool n' Quiet feature that ramps CPU voltage & speed down when not needed. Slower models run a whole lot cooler. Bigger HS capability than with Athlon XP. 64-bit processing an obvious bonus. Probably the best quiet & powerful option right now. Mar/04

Intel Celeron P4 (Northwood 2-2.2 GHz)

70-74W Estimated max power. Large HS capability of P4 form factor helps. 20/7/02
AMD XP/MP T-bred "B" 2400+ to 2800+ (2.0-2.25GHz)
The 68W max power of the 2800+ is the same as the T-bred A 2100+ running 333 MHz slower. Undervolting/clocking or slower B versions should drop power dissipation enough to at least move them into the 5-rank. Mar 7/03
AMD XP/MP T-bred "A" 2000+ to 2200+ (1.66-1.8GHz)
55-62W typical power in the fastest of these first T-breds difficult to cool quietly due to small heat transfer contact area. 1/08/02
AMD XP/MP Palomino 1500+ to 2100+ (1.33 - 1.73 GHz)
Improved efficiency over T-bird mitigated by higher clock speeds; typical power ranges from 54W for 1500+ to 64W for 2100+. Unlocking of multiplier more difficult but can be achieved. Requires at least Q8 ranked HS. 20/7/02

Intel Celeron Willamette (1.7 - 1.8 GHz)

1st generation 0.18µ P4 core w/128KB cache 2, 57~61W heat dissipation. Only larger HS capability saves this model from lower rank. A big step down in every way from the Tualatin 0.13µ 370 Celeron. 20/7/02
Intel PII Klamath core (233-300 MHz)
Early P2 with less efficient core difficult to cool quietly, as power dissipation is 35-43W, and good quiet HS hard to find. With slow performance, not much incentive. 20/7/02
Intel P4 (A, C, G) Northwood (2.6-2.8 GHz)
"Typical power" ratings of 63-70W; requires large powerful heatsink to run with a quiet fan & good case airflow. 20/7/02
AMD XP Barton 3000-3200+
68~77W max at this speed, still can be cooled reasonably quietly with careful case airflow and powerful HS. Mar 7/04
Intel P4 Willamette core (1.3-2.0 GHz)

3 - 4

Early P4s with typical power from 49W to 75W, these hot processors are difficult to cool quietly, despite the large HS form factor. Serious undervolting and underclocking may work. Thermal protection throttles speed under high loads so maximum power (100W for 2GHz) may never be reached. Thus, these (and all P4s) very tolerant of thermal abuse. 20/7/02
Athlon 64 FX-51
89W; new arrangement for bigger HS. Mar/04
Intel P4 (C, G) (3.0 - 3.4 GHz)
"Typical power" ratings of 82~89W are big challenges to quiet, but it can be done, not cheaply. Mar/04
Intel P4 EE (E, G) (3.2 - 3.4)
2 - 3
92~103W "Typical power". Not much more to say. Mar/04

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