The best tool as yet available to read/write and examine the special 6x86 registers was written by Koen Gadeyne and is now maintained by yours truly; it is called set6x86. The latest version of this patch/utility combo is version 1.5. It should be available from sunsite.unc.edu in the /pub/Linux/system/hardware directory. The set6x86 utility proper is command-line driven, and is able to set/reset any specific 6x86 flag/register/feature.
The set6x86 tar.gz package also includes a very handy rc.cyrix script that can be used to enable most useful features at boot time, by calling it from rc.local. These are the lines I added my /etc/rc.d/rc.local file:
# Cyrix CPU configuration
if [ -f /etc/rc.d/rc.cyrix ]; then
Set6x86 will work equally well with all 6x86, 6x86L and 6x86MX equipped GNU/Linux boxes.
The main change in set6x86 versions 1.4 and 1.5 is that they now include a small kernel patch and also an updated debugging utility to display not only the Address Region Registers but all the relevant 6x86 registers in human-readable format. Version 1.5 will also report the bogoMIPS ratings, as calculated by the kernel during boot time and also as independently calculated by 6x86_reg. This may come in handy for people with some odd motherboard/BIOS combinations.
You can download a copy of the set6x86 version 1.5 combo patch/utility using the HTTP protocol by shift-clicking on this link (27Kb): set6x86-1.5.tar.gz.
If you want to tinker with your new toy, you may want to try an Xforms front-end to set6x86 called f6x86, written by Ian J. Peters, also available from sunsite.unc.edu in the same directory as above. However, f6x86 was designed for set6x86 version 1.0 (which is included with the f6x86 package), not 1.5, so beware. Here is what the main window looks like:
And the ARR settings screen is:
Both set6x86 and f6x86 are under GPL.
Greg Kondrasuk has recently updated his OS/2 port of set6x86 to version 1.5. It can be found at ftp://hobbes.nmsu.edu/pub/os2/util/system/set6x86.zip. Nice job, Greg!
There is also a shareware DOS package called 6x86opt by Mikael Johansson, which has lots of useful information on how to setup some performance enhancing features of the Cyrix 6x86 CPUs.
To experiment with optimizing the performance of your 6x86 system, read the Application Notes and Data Books for the 6x86 processors, use set6x86 to change CPU settings and then run some short benchmarks.
The best document describing 6x86 configuration settings for maximum performance is IBM's Application Note 40205 "IBM 6x86 Microprocessor BIOS Writer's Guide" available in both HTML and PDF formats from IBM's site (see Docs & Links page). A similar document is available for the 6x86MX from the Cyrix site: "Application Note 103 - 6x86MX BIOS Writer's Guide".
Last updated on January 5, 1998.
Copyright 1997 Andrew D. Balsa