bob2, what a guy! Old tech help for the K6-2.

bob2 gave me this old Biostar Pentium motherboard, the 8500TURD, er, 8500TTD board, great news!
OK, I looked the board up and found that Revision 1.3 and newer supported K6-2's with a BIOS update :smile:
But then I got it and it was revision 1.2 :frown:
So I poked around with a probe and found one transistor who's sink was the same as the core voltage, so...
There were two jumpers missing from the 1.2 to prevent lower voltages :frown:
But I found the solder point for one of them, stuck a screwdriver across it, and it droped the voltage to the right reading :smile:
I soldered in the jumper and updated the BIOS :smile:
But then I got a weir BIOS error with a K6-2 :frown:
So I reflashed the BIOS a again, but this time included boot block, and it worked :smile:
But the CPU wouldn't boot at 2.18v, which is the reading I got with it set to 2.2v :frown:
So I poked around again, and here is what I found:
With only the new jumper installed, I get 2.1v, so the board now supports K6-2+ and K6-3 processors :smile:
Leaving the new jumper installed, adding the first jumper gives it 2.2v (2.18 measured), the second 2.4v (2.32 measured), the third 2.5v (2.48 measured), so all these undocumented voltages...are the same as the entire line of K6-2s :smile:
This CPU runs perfectly using 2x=6x and 2.32v using the 2.4v setting, supporting 450MHz at 75MHz bus :smile:

Now, I could have simply used the 2.8v setting and an Athlon/PIII typed cooler, but why do that when this thing runs perfectly with the CPU at a lower voltage, with a small cooler?

The board supports up to 512MB of PC133!!! Thanks bob2!!!

<font color=blue>You're posting in a forum with class. It may be third class, but it's still class!</font color=blue>
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  1. thats gotta be the record for smileys in one post!


    <i>It's always the one thing you never suspected.</i>
  2. Lmao....sounds like a cool lil project...just curious Crash but what is your major at U of M ?...I have a girlfriend that goes there :smile: that is an EE...
  3. LOL, nice problem solving. That would have driven most people insane. In fact, I'm feeling a little goofy after just reading it. :)

    ---There may be more than one way to do it, but why would anyone want to remove the fur from a feline?---
  4. Crashman is no longer is school, Crashman is an unemployed mechanical designer/SDRC CAE package specialist.

    <font color=blue>You're posting in a forum with class. It may be third class, but it's still class!</font color=blue>
  5. Join the club. I'm an unemployed Graphic Designing Engineer! Ran Unigraphics for a long, long time for GM. Appears the Mexico is now doing our work. 1500 of us went out between Ford, GM & Chrysler. Sweet Huh? I can go to work in Teluca Mexico, but can't find a job in my own country. Been out a year now. Could be worse, I always say!!!!

    I'm still learning & having fun doing it!! Trouble comes with the things you forget or overlook along the way that make it not so fun!!
  6. Crash,

    Would this trick be possible on the Biostar 8500 TUC, V3.2?

    I've got it stashed in the basement, waiting for me to get the courage to try my K6-2 at 2.8V.

    If you've got any pictures of how and where you jumpered yours, maybe I can figure it out with my TUC.

  7. I've got good news! That is, that I've actually sold around 30 or more systems with the K6-2 at 2.8v using a large cooler, and none have come back with a burned CPU. Of course, if you had a meter, you could set the 2.8v setting on some old pentium chip (doesn't matter if it boots or not) and poke around to find a good 2.8v source, set it back to 3.4v and check to see if that source went to 3.4v, and then play with the VRM jumpers until you find an adequate setting!

    Anyway, 2.8v or less will work with proper cooling. And the 133MHz setting will work for 400MHz because of AMD's built in 2x=6x feature.

    <font color=blue>You're posting in a forum with class. It may be third class, but it's still class!</font color=blue>
  8. I'll give it a try. I've got a Pentium 200MMX in it now, and an old Cyrix 150 that I can definitely sacrifice.

    Memory will be my speed limitation as it only has 64mb of EDO. Should be OK for Win98 and old DOS games for the kids, etc.


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