Den Frie Vilje Discover Hotfix
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For Windows

HotfixOur first Windows release. You are here.

For the Mac

BoomerBlasterA silent disco for the open-plan office docksteadyKeeps identical displays where you put them cupertino-filesPages, Numbers and Keynote files in TypeScript
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Hotfix 0.1.1Free
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Hotfix

It's warmer on Windows

Den Frie Vilje's first Windows release turns the processor and graphics time your PC isn't using into heat for the room. The moment you need the power back, it's yours.

Free. For 64-bit Windows 11 and Windows 10.1

Every watt a PC draws ends up as heat in the room it stands in. Your PC has always been a heater. Hotfix just gives it something to do.

The Hotfix difference

Warmth from the PC you already have

No radiator to buy and no socket to find. Hotfix lives by the clock and puts your processor and graphics card to work warming the room: about 250 watts on the PC it was made on.2

Steps aside while you work

Twice a second, Hotfix checks how busy your other apps keep the PC. Start a build and the heat drops at once. When the build finishes, the warmth climbs back over ten seconds.

CPU and GPU, each on its own

The processor and the graphics card yield separately, and in proportion. Fill the GPU with a scene and the CPU keeps you warm. Fill half the cores and Hotfix warms with most of the other half.

Nothing to sign in to

No account, no cloud, no telemetry. Hotfix makes no network connections at all, which is unusual for something this warm.

Our first for Windows

Den Frie Vilje has made software for the Mac for years. Hotfix is the first thing we have shipped for Windows, so we started with the part of a PC that Mac people ask about most.

Say hello to warmth

No need to remember your gloves. Sign in with your face, fingerprint or PIN as usual. The keyboard is already warm.3

Explore how it steps aside

For once, Very high is a good thing

Task Manager rates Hotfix's power usage Very high. Then you start working, and it isn't. Try it.

Task Manager
Type a name, publisher, or PID to search

Processes

NameStatus0%CPU41%Memory0%GPUPower usage
Apps (3)
Hotfix0%58.2 MB0%Very low
Your build0%0 MB0%Very low
Your scene0.1%1,204 MB0%Very low
Background processes (2)
Desktop Window Manager0.8%88.0 MB2.1%Very low
Your 41 browser tabs2.4%6,214 MB0.9%Low

Simulated in your browser, with the same rules Hotfix follows.4

Hotfix vs. others

Hotfix Other major heating systems
FlexibilityUses the PC you already haveRequires a separate appliance
CompatibilityWorks with your apps, and steps aside for themMay require a free socket5
Local heatGenerated on device. No cloud required.Heat varies by radiator
GamingSteps aside for every PC gameFewer PC titles to choose from
SecurityCollects nothing. Connects to nothing.Varies by landlord

Choose the Hotfix that's right for you

Save 0% when you pay yearly for Hotfix.

Save 0 kr. with a yearly plan

Hotfix Personal

0 kr./year0 kr./month

Hotfix Personal includes:

  • For 1 person
  • Warm with CPU
  • Steps aside while you work
  • Start with Windows
DownloadOr try free for one winter
Save 0 kr. with a yearly plan

Hotfix Family

0 kr./year0 kr./month

Everything in Hotfix Personal, plus:

  • Warm with GPU
  • For 1 to 6 people, if they sit close6
  • CPU and GPU, each on its own
DownloadOr try free for one winter
Save 0 kr. with a yearly plan

Hotfix Premium

0 kr./year0 kr./month

Everything in Hotfix Family, plus:

  • Den Frie Vilje's first Windows release, at no extra cost
  • The same file as the other two7
DownloadOr try free for one winter

Will Hotfix run on my PC?

Operating system
64-bit Windows 11, or Windows 10 version 1903 or laterTested on Windows 11 version 25H2
Processor
Any x64 processorAVX2 and FMA make it warmer: Intel since 2013, AMD since 2015
Graphics
A DirectX 12 graphics card, for Warm with GPUWithout one, Hotfix warms with the CPU alone
Heat
About 250 W on the PC it was made onAbout 140 W from an Intel Core Ultra 7 265K and 110 W from an NVIDIA GeForce RTX 5070 Ti, above idle2
Storage
About 120 MBHotfix brings its own copy of .NET, so there is nothing else to install
Administrator rights
Not requiredHotfix installs for you only
TPM 2.0
Not requiredWe checked twice
Microsoft account
Not requiredOr any other account
Internet connection
Not requiredNot used, either
In the box
Hotfix, an icon by the clock and a menu with five itemsNot in the box: a radiator, Copilot
Licence
MITSource code on GitHub

Den Frie Vilje Research · Blog

Toward maximally useless computation

How we searched for the calculation that heats a room best and means least, and found one whose answer is as close to nothing as a processor will compute at full speed.

Thermal Computing groupPublished 14 October 2026
  • Systems and networking
  • Thermodynamics
  • Office comfort

For as long as computers have run warm, the field has asked what they should compute. We asked the opposite question. Hotfix turns electricity into heat by keeping a PC's processor and graphics card busy, and the heat does not depend on what they compute. If the result is going to be thrown away anyway, how little can it mean?

Method

We held each candidate to three criteria. It must keep every arithmetic unit busy, so that no watt goes unspent. It must stay on the fast path, so that no watt is lost to waiting. And its answer must be as close to nothing as possible, so that no meaning escapes into the room.

Results

CandidateSettles onProcessor9Graphics cardVerdict
Doing nothingNothingIdleIdleRejected. Cold.
x × 0.9999999 + 0.0000001Hotfix 0.1.0, processor0.58886087, after 9.3 million steps121–122 WRejected. 0.58886087 is not nothing.
The same, eight chains summedHotfix 0.1.0, graphics cardInfinity, after 43 passes, about a seventh of a second170–171 WRejected. Infinity is the opposite of nothing.
x × 0 + 0ZeroNot builtRejected. A shader compiler may delete it, and a multiplier given nothing to do does very little of it.
Anything settling below 2−126A subnormal numberNot builtRejected. Processors slow down for subnormal numbers and graphics cards flush them to zero. Both make less heat.
x × ½ + 2−126Hotfix 0.1.12−125, within about 150 steps126–130 W163–170 WSelected.
Table 1: Candidate calculations, their answers and their heat.

The calculation

Each processor thread runs eight independent chains of eight floats, a million steps at a time between checks on whether you need the core back:

C#
a = Vector256.FusedMultiplyAdd(a, half, tiny);  // a * 1/2 + 2^-126

The graphics card runs the same in a compute shader, eight chains per thread and two million threads per pass:

C#, compiled to HLSL
a = a * 0.5f + 1.17549435E-38f;  // 2^-126, the smallest normal float

From anywhere sensible, each step halves the distance to the answer, and every chain lands on it within 150 steps. From then on:

2−125 × ½ + 2−126 = 2−126 + 2−126 = 2−125

Every multiply-add returns exactly the number it was given. Written out, that number is

0.000 000 000 000 000 000 000 000 000 000 000 000 023 509 887

Theorem 1 (no smaller nothing). A calculation x × m + c with a multiplier m between 0 and 1, in which every value is a normal 32-bit float, cannot settle on an answer smaller than 2−125 in size.

Proof. At its answer, x = m·x + c, and both terms have the same sign as x. Both are normal floats, so each is at least 2−126 in size, and x is at least 2−125. ∎10

Throughput

On an NVIDIA GeForce RTX 5070 Ti, Hotfix computes 2−125 21.5 trillion times a second. It makes about as much heat on the graphics card as infinity did, and a little more on the processor. Nobody has ever asked for the answer.11

Looking ahead

We are considering lending the same watts to climate science (Hotfix 2), and warming only while electricity is cheap and clean (Hotfix 3). Both would be steps backwards for this line of research.

Publication

Toward maximally useless computation Technical report DFV-TR-2026-01, Den Frie Vilje Research, 2026. PDF, 4 pages.
Download the paper (PDF)Read it in your browserReproduce the results
Cite this
@techreport{dfv-tr-2026-01,
  title       = {Toward Maximally Useless Computation},
  author      = {{Thermal Computing group}},
  institution = {Den Frie Vilje Research},
  number      = {DFV-TR-2026-01},
  year        = {2026},
  note        = {The answer is $2^{-125}$},
  url         = {https://den-frie-vilje.github.io/hotfix/paper/DFV-TR-2026-01.pdf}
}

Hotfix › Troubleshooting

The office is cold

Applies to Open-plan officesWindows 11Windows 10Your fingers

Symptoms

You are wearing a jumper indoors. Your typing has slowed. A colleague has mentioned the thermostat twice since lunch.

Cause

This problem occurs because someone else controls the heating, while your PC's processor and graphics card spend most of the day idle.

Resolution

To resolve this problem, install Hotfix:

  1. Download Hotfix-win-Setup.exe.
  2. Open it. If Windows shows Windows protected your PC, select More info, then Run anyway.12
  3. Wait. Hotfix starts warming at once, and turns itself down whenever you work.

Status

Den Frie Vilje has confirmed that this is a problem in the offices listed in the Applies to section.

More information

To change what Hotfix warms with, select its icon in the notification area. To uninstall it, go to Settings › Apps › Installed apps.

Was this information helpful?

Questions about Hotfix?
Start here.

What is Hotfix?

A small Windows app that keeps your processor and graphics card busy with arithmetic, so that the electricity they draw warms the room you are sitting in. It lives in the notification area and has a menu with five items.

What does Hotfix compute?

As close to nothing as a processor will compute at full speed: 2−125, over and over, about 21.5 trillion times a second on the graphics card it was made on. Den Frie Vilje Research explains how it was found.

Will Hotfix slow down my work?

Hardly. Hotfix runs at the lowest priority Windows has, on the processor and on the graphics card, so your work always goes first. That alone is not enough, because a chip that is kept hot clocks lower, so Hotfix also turns itself down while your apps are busy and back up when they are quiet.

On the PC it was made on, single-thread work ran no slower with Hotfix warming than without it. Work that fills your processor or your graphics card makes that half of Hotfix stand down altogether, and the other half carries on.13

How much heat does it make?

Whatever your PC can draw. On the PC Hotfix was made on, it adds about 140 W from the processor and 110 W from the graphics card: 250 W, a quarter of a small fan heater. A laptop makes much less.

Is it efficient?

Exactly as efficient as any electric heater: every watt becomes heat. A heat pump does three to four times better, if you have one and are allowed to touch it.

At 250 W for an eight-hour day, Hotfix uses 2 kWh. At 2.50 kr. a kWh, that is 5 kr. a day.

Is it safe for my PC?

Hotfix asks no more of your PC than a long render or a game does, and it never changes a clock, a voltage or a power limit. Processors and graphics cards protect themselves from heat by slowing down. Your fans will be audible.

Does Hotfix work with Copilot?

No.

Can I use it at work?

Ask whoever pays for the electricity. Hotfix installs without administrator rights, which is not the same thing as permission.

How do I uninstall Hotfix?

Go to Settings › Apps › Installed apps, select … next to Hotfix, then Uninstall. Its Start with Windows entry and its settings go with it.

Why is Hotfix Den Frie Vilje's first Windows release?

Someone in the office was cold, and the PC under their desk had a graphics card in it.