Tyan S1590 and the AMD K6-III+

The text presented here documents my finding while trying to get a K6-III+/450 to work in my Tyan S1590 motherboard. It should also be stressed that I have only done this on a single system. I can not attest to the long-term stability or the compatibility of the K6-2+ and the S1590.

When installing a K6-2+ or K6-III+ in a Tyan S1590 motherboard you have two options. The first is to flash upgrade the BIOS to a version modified by Jan Steunebrink.
The second is to set the clock multiplier jumpers to 3x and use software to optimize the processor and increase its internal software controlled clock multiplier.

The patched BIOS is available at

Utility programs are available at Although I originally used the second option (3x multiplier and utility programs) I am currently using the patched BIOS. This is by far the cleanest solution and does not require other processing of programs in your AUTOEXEC.BAT file. I must state however that this BIOS version is not from Tyan and thus is not likely to be supported by them.

Additionally my S1590 is of the earlier 4 jumper V-core selection series.
Although 2.0V is listed in the manual as an available V-core setting it produces 1.25V when selected. As it turns out this is exactly what the Cherry Semiconductor switching voltage regulator (CS5151) used on my S1590 is designed to generate. The 5 jumper V-core version of the S1590 apparently does not suffer from this limitation because it uses the CS5155 or CS5156 which has a wider voltage selection (that includes 2.0V).

At any rate I had to set the core voltage to 2.1V.
With the patched BIOS and this core voltage setting I am running at a multiplier of 5.5 with an FSB of 100MHz.

As I mentioned previously the K6-III+ (and K6-2+) have the ability to change the clock multiplier on the fly.
A few applications are available (DOS and Windows based) that allow you to do this. The first of these utilities (which I originally used) is the DOS based application TSC.EXE.
This application is run from your AUTOEXEC.BAT file each time you start your Windows based system.
The second utility (which I currently use) is a combination DOS and Windows based program set. The first component runs at the DOS level (in the AUTOEXEC.BAT) file to prepare it for software switching.
Then a Windows based component can be run to select one of the available clock multipliers. This program set is available at

The third utility is run completely from Windows and does not have a DOS based component. Additionally it has built in features for optimizing other areas of the processor. This utility is available at I must state that I have not tested this utility myself and can not attest to its functionality. However I have read reports that indicate that it functions nicely. I have not used it since the patched BIOS I'm using already performs the necessary configuration of the processor.

When running with the K6-III+ the Tyan System Health Monitor incorrectly reported voltage and temperature measurements (at least on my system).
The System Health Monitor reports erratic and out of tolerance voltages and temperatures as the clock multiplier is changed.

Using a multi-meter I verified that the core voltage was not changing and was stable at the 2.1V setting I selected. This was also the case for other voltages (3.3V and 5.0V).
The datasheets for the K6-2+ and K6-III+ specify a recommended operating core voltage of 1.9V to 2.1V. The absolute maximum rating as listed in the datasheet is 2.2 volts.

I also taped a temperature probe to the backside of my K6-III+ (same side the onboard temperature sensor is located). Then I compared the temperature meter to the temperature reported by the System Health Monitor (SHM). I then ran the Mad Orion benchmark program (default benchmark) with the CPU at 600MHz.
The temperature meter peaked at 43C, while the SHM program jumped all over and got as high as 70C.

The SHM program would show large fluctuations in very short time periods (as much as 10C between readings). While the temperature meter showed much slower fluctuations in temperature (0.2C between readings). This leads me to believe that the onboard voltage and temperature monitoring on the S1590 does not work well with the K6-III+.
I never performed this test using a K6-2, so can't attest to its accuracy with that processor. I performed this test on just one S1590 motherboard. So I can't definitively say others are also inaccurate. In my case the SHM program is not correct. The temperature of the CPU is well within tolerance.

I have however noticed that the temperature and voltage measurements of the SHM do not fluctuate nearly so much when running a CPU cooler program.
For example Rain, available at

As mentioned earlier I originally had the AMD K6-III+ running in my Tyan S1590S with the 1.16C BIOS available from the Tyan web site. Using this BIOS I had to set the multiplier to 3.0 via jumpers (anything higher and it would not start up). However I could step the multiplier up via the TSC utility in AUTOEXEC.BAT.
I also tested this using earlier BIOS revisions with the same results.

When using the Tyan supplied BIOS I am able to resolve any incompatible issues via utility programs in my AUTOEXEC.BAT file (available at the above links).

The following is an excerpt from my AUTOEXEC.BAT file (prior to using the patched BIOS)

C:\AMDK63\TSC 5.5
C:\AMDK63\K6WAON 128
Note: EMM386.EXE must not be loaded in order for these utilities to operate properly.

Michael McCarrick

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