KATE(4)

💅 KATE(4) — the AMD K8 temp sensor page, explained by your favorite Unix bestie

okay so this is from the Kernel Interfaces Manual (section 4, which is like, drivers and kernel stuff, iykyk) and we're talking about kate — the AMD K8 temperature sensor. yes she's named kate. yes she's iconic. let's go 🎀

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✨ NAME ✨

kate — the AMD K8 temperature sensor, fr fr

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🌸 SYNOPSIS 🌸

kate* at pci?

that's it. that's the whole vibe check. she attaches at pci? and that asterisk means "one or more of her, depending on how many chips you got" 🦋

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🔥 DESCRIPTION 🔥

The kate driver provides support for the temperature sensors that live inside the AMD K8 family of processors. she's literally just here to tell you how hot your CPU is being. main character energy 💅

So these sensors were officially introduced with Revision F Family 0Fh processors, and they give you 1 degC accuracy. cute, but the glow-up came with Revision G chips, which added two more bits so you get 0.25 degC steppings. precision queen 👑

Each core may have two temperature sensors, and there may be up to two cores per package. so the math is mathing in a kinda fun way.

Multiprocessor systems get one instance of kate per each chip. In each instance:

• temp0 and temp1 are the sensors on the first core
• temp2 and temp3 are the sensors on the second core

As such, single core chips may have two sensors, and dual-core dual-processor systems may have as many as 8 temperature sensors in total. eight!! she's booked and busy 🫶

Now here's the little plot twist: since many prior revisions of the chips appear to have valid readings for at least some temperature sensors in the same address space as the aforementioned revisions, the driver may also attach on such older revisions — provided that it finds some sensor readings that appear valid. lowkey lenient of her, honestly.

⚠️ But in such cases kate would not print the core revision information into the dmesg. so don't come for her when the revision info is missing, she warned you 😭

Sensor values are made available through the sysctl(8) interface. that's where you go to peek at the numbers 💖

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🦋 SEE ALSO 🦋

• intro(4)
• pci(4)
• sensorsd(8)
• sysctl(8)

and the reading list, because she's studious:

• BIOS and Kernel Developer's Guide for AMD NPT Family 0Fh Processors, Publication # 32559, pp. 21–23 and pp. 179–184, July 2007.
• Revision Guide for AMD NPT Family 0Fh Processors, Publication # 33610, February 2008.

like she did the homework. respectfully. 📚✨

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👑 HISTORY 👑

The kate driver first appeared in OpenBSD 4.4. a legend was born, etc etc 🌈

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💜 AUTHORS 💜

The kate driver was written by Constantine A. Murenin <cnst@openbsd.org> whilst at the University of Waterloo. ok stan a little bit 🍓

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and that's the whole page bestie — every flag, every degree, every sensor accounted for, no cap 💀

shoutout to the Debian packaging of this page, dated April 23, 2019 — that's the source/version + date energy, mwah 😘