Linux kernel patches

An experimental kernel patch was originally written by Mike Jagdis. However, this experimental patch is not being regularly maintained by Mike anymore. I have asked Mike and he agreed in principle to have his patch and mine merged into a single Cyrix patch. So you will find an abridged version of the documentation included with his patch in the set6x86 version 1.5 patch/utility combo.

My latest Cyrix patch, which I believe is compatible with all 2.0.x kernels and most 2.1.x kernels, is a very short patch that must be used with set6x86 version 1.5 for optimum performance and protection against the 6x86 coma bug.

This patch will:
1. Correctly reset the 6x86(L) SLOP flag so that bogomips are _always_ correctly calculated on boot (on 6x86 CPUs, bogomips should be reported as the core clock rate +/- 1 MHz).
2. Correctly identify and report _all_ 6x86 CPU models and steppings in /proc/cpuinfo.
3. Workaround the oops caused by time.c when handling 6x86MX chips.
This patch will _not_:
1. Implement the experimental VSPM paging, since this has proved of little use in real-world settings.
2. Add any more options to the kernel config script.
3. Set any performance features (use set6x86 to experiment with these).
4. Set SUSPEND_ON_HALT. Again, this option can be set with set6x86 for lower power consumption when the CPU is idle; note that in some rare cases setting power-down mode is not recommended.
5. Address the 6x86 coma bug. Using set6x86 to set the NO_LOCK bit is at the moment the recommended solution.

Patch installation

• Copy the patch to /usr/src or wherever you have your /linux source tree.
• Make a backup of your kernel source tree.
• Apply the patch against your kernel source (man patch if you don't know how to do this).
• If any error messages appeared during patching, check to see what went wrong. Usually it's some small detail that prevents patch from doing its work, but can be corrected manually in a few seconds.
• RTFM (Read The Fine Manual/Documentation).
• Recompile the kernel with e.g. make dep; make clean; make zImage.
• Install with e.g. lilo.
• Reboot.
• Check /proc/cpuinfo. Your Cyrix 6x86 is now correctly identified :-)

As stated in the Introduction page, I believe the Linux kernel source should be kept as "clean and tidy" as possible, so I will not respond to requests to add more features to my patch. There is one important disadvantage of kernel patches for configurable parameters: every time one wants to modify an option, a kernel recompilation is needed. Since it takes a few seconds to modify an rc.cyrix script, I am convinced it's better to have all the options set by set6x86.

I'll quote Antoine de St. Exupéry, as quoted by Andrew Tanenbaum in his book "Structured Computer Organization" (third ed., Prentice Hall):

"Perfection is achieved, not when there is nothing left to add, but when there is nothing left to take away."

Downloading

For kernel versions 2.0.x and 2.1.64-, my short patch with CPU model and stepping identification is available here (8Kb). But you should really download the set6x86 version 1.5 package (26Kb), which includes the patch.

For kernel versions 2.1.65+, Stéphane Casset has contributed a modified version of my short Cyrix patch (also 8Kb).

Last updated on December 14, 1997.

Copyright 1997 Andrew D. Balsa