chys's random notes » hardware

Intel announces AVX2

chys — Tue, 14 Jun 2011 06:38:01 +0000

The documentation is available for download.

The instruction set war is still there – Intel still doesn’t plan to support many XOP features of AMD; also Intel still plans to use FMA3 while AMD uses FMA4. Nevertheless, this time Intel is at least not making the war even worse. In addition to extending most SSE2/SSE3/SSE4 instructions to 256 bits (this is no surprise), they copied BMI (with an extension called BMI2) and CVT16 from AMD. If I recall correctly, Intel had never copied so many instructions from AMD at once, with the notable exception of x86-64.

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CPU Frequency Governor

chys — Fri, 21 May 2010 14:29:26 +0000

Kernel documentation recommends “conservative” for laptops, citing latency reasons.

However, Intel explicitly recommends “ondemand” in its powertop. So does at least one Intel kernel developer.

OK. I have been using “conservative.” I decide to switch to “ondemand” from now on.

Reference

gspca in Linux 2.6.27

gspca in Linux 2.6.27

chys — Sat, 10 Jan 2009 05:14:00 +0000

only works with v4l2, but not v4l. So it can lead to problems – programs using v4l gives strange pictures as well as annoying error messages.

My webcam worked with gspcav1 and Linux 2.6.26, but it failed in Linux 2.6.27 (with its in-kernel gspca drivers):

>>cmcapture err -1
cvsync err
: Invalid argument
cmcapture: Invalid argument

Solution: Install libv4l, and use a command like this:LD_PRELOAD=/usr/lib/libv4l/v4l2convert.so skype.

Reference
Linux kernel bug #11860.