With the Tyan Tomcat (I-III) series, the most recent (as of early 1999) BIOS is Award v 4.02. This version is K6 "aware" in that it turns on the write-allocate feature automatically when any AMD K6 is detected, and knows of and makes available the 3DNow! instructions for the K6-2. The PowerLeap CPU Control Panel software is not needed in this case for the write-allocate or 3DNow!. However, the PL software is still needed if you wish to use the temperature sensing and cpu clock slowing features of the CPU Control Panel.
For those using v 4.01 and previous BIOS for the Tomcat (I-III), you will need to use the PL CPU Control Panel software to achieve maximum performance with your K6-2. At 333 MHz (66.67x5.0) with the v 4.01 BIOS, I found the CPU Control Panel software made only a 1-2 percent improvement in CPU scores as measured with Wintune97 (618 to 630) and Wintune98 (797 to 807). Video scores rose much more dramatically with Wintune98, going from 41 MP/s to 44 MP/s (almost a 10 percent increase) by adding the write-allocate "on." With the v 4.02 BIOS, I get the same results without the PL software running, which also helps pure DOS programs (the PL software runs only under Windows 9x, to the best of my knowledge, and thus will not help a program running under a re-boot to MS-DOS mode).
Please note there are newer versions of the K6-2 using the
K6-3 core. The newer core seems to have its write-allocate
registers in different places, and my suspicion is that the v
4.02 BIOS will not work properly with the new K6-2 core. In this
case, you must use the PL software and the work-arounds they have
posted to date to get the write-allocate to work properly. The
new core CPUs seem to have steppings of 08 and higher. The 00
stepping has the old K6-2 core (what I have). The newer cores
offer greater speed when properly used by the BIOS or CPU Control
Panel. I have hopes that Tyan will upgrade the BIOS for the
earlier Tomcats to work properly with the new K6-2 and K6-3 (but
we'll see...).
Many thanks to Frank Gracie
for his help on the BIOS issues discussed above for this
motherboard. Frank also has informed me that the information
above is applicable to the Tyan Tomcat IV, but with BIOS versions
1.02 equivalent to v 4.02 above, and 1.01 for the Tomcat IV
equivalent to v 4.01 for the Tomcat I-III.
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This page last updated 3/10/99