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#51113 by cp
Tue Nov 25, 2008 9:19 pm
this poor little mainboard has been bugging me quite a while now. there are options in the bios to change the FSB but once set to something different than 66 MHz or AUTO, the board refuses to boot. i suspect the i2c data written to the pll doesn't quite fit. changing around some bios versions didn't help much and there's no information on the pll available. the pll is an ELITE 9248AF-59 which is obviously an ICS 9248AF-59. doesn't help that much since there's no datasheet available. but right next to the pll there are four resistors arranged in a matrix and they look just like...yes! pull-up/-down resistors.

the first pad in each row is connected to +5V, the last pad in each row is connected to GND and the pads in the middle are connected to the pll. the matrix - showing the factory default - looks like this :

Code: Select all r is a 10k resistor
 * is a pad
 - is a trace

 +5V    GND
  |      |
  v      v
4 *r*--* *
3 * *--*r*
2 * *--*r*
1 *r*--* *


so the default setting is from 1 to 4 : 1001 which results in a 66 MHz FSB.

the cool thing is: the config pins have internal pull-up resistors which means that if you don't connect the middle pad anywhere the result will be a 1. very good for the lazy ones around :)

okay, after some fiddling around with the resistors here is the table so far:

Code: Select all1 means pulled up so either connected to +5V via 10k or unconnected
0 means pulled down to GND via 10k

1 2 3 4 FSB
0 0 0 0  90
0 0 1 0  66
0 1 1 0 100
1 0 0 1  66
0 0 1 1  75
1 0 1 1  95


the rest of the settings resulted in a non-booting system but if i get my hands on a 133 MHz coppermine PIII i'll do some more tests.

currently my board is running a celeron coppermine 733@1100 with a 100 MHz FSB. much better than the original 733/66 setup :)