Arch Linux

Painless

Member

Registered: 2006-02-06

Posts: 233

microcode_ctl

Hi all,

This is not a problem, just a question.

I noticed a recently updated package, microcode_ctl, and I was wondering, what does it actually do?  The official website has a somewhat esoteric description:

* it decodes and sends new microcode to the kernel driver to be uploaded to Intel IA32 processors. (Pentium Pro, PII, PIII, Pentium 4, Celeron, Xeon etc - all P6 and above, which does NOT include pentium classics). It also supports processors of the x86_64 architecture.
* it signals the kernel driver to release any buffers it may hold

And I found a man page which says pretty much the same thing:

a) it decodes and sends new microcode to the kernel driver to be uploaded to Intel IA32 processors. (Pentium Pro, PII, Celeron, PIII, Xeon, Pentium 4 etc)

b) it signals the kernel driver to release the buffers containing the copy of microcode data actually applied to given CPU, linear array of 2048 bytes per CPU, see struct microcode in include/asm/processor.h for information on the layout of chunks buffers may hold

What I'd like to know is: What effect does it have on a PC (running an appropriate CPU)?  Does it make that PC faster, more responsive?  What does the end user see?  What is it actually for?

Thanks in advance for any light you guys can shed on this! 

Last edited by Painless (2008-04-03 16:13:28)

brebs

Member

Registered: 2007-04-03

Posts: 3,742

Re: microcode_ctl

Put simply:  It fixes bugs in the CPU, by uploading better microcode. So the end-user will see less crazy behaviour by the PC.

The CPU most likely still has known bugs, though

brain0

Developer

From: Aachen - Germany

Registered: 2005-01-03

Posts: 1,382

Re: microcode_ctl

The "bugs" it fixes have most likely been reproduced only in a laboratory and will probably never occur in real life. Some vendors also provide BIOS updates which upload the new microcode on boot. If you cannot update the BIOS (like me for example: the update utility is only available for Windows and I wiped that from the hard drive), microcode_ctl is your only way of getting a fixed microcode. If you have an Intel Pentium Pro or newer (that means ANY Intel CPU that is capable of running Arch), then runnuing microcode on boot is not a bad idea.

BC

Member

Registered: 2008-01-29

Posts: 83

Re: microcode_ctl

The microcode is absolutely vital for stablilty on one of my PCs.  I couldn't get an uptime of more than a hour without it.

Painless

Member

Registered: 2006-02-06

Posts: 233

Re: microcode_ctl

Thanks for the replies.  I guess I can just about forgive Intel for not directly saying:

It fixes bugs in our hardware