I assume this is likely an OEM board that was contracted out to Abit. Rather interesting.

Save the BIOS today!

BIOS INFO - 694X-686B-6A6LJA1LC-YJ
BIOS DATE - 03/05/2001
BIOS CHIP - AMIC A29002 /5V
BIOS CHECKSUM - 8223H

I checked it with Celeron 900MHz (100MHz), 1.75V SL5MQ. The positions of the switches that set the FSB and got just such a table.

Some hi-res photos of mobo, signal pins and external USB connector.
Continue to test it with PIII 1GHz, 1.75V Coppermine CPU.

Clock generator looks like a PLL202-11, datasheet here: http://www.abcelectronique.com/composants/tel … mber=PLL202-11D
Seems to pretty much match the table you worked out:

1SW3 SW2 SW1 - CPU    PCI
2on  on  on  - 80     40.0
3on  on  off - 75     37.5
4on  off on  - 83.3   41.7
5on  off off - 66.8   33.4
6off on  on  - 103    34.3
7off on  off - 112    37.3
8off off on  - 68     34.0
9off off off - 100.2  33.4

From your table then SW4 doesn't change the frequency so may not be connected even though there is an FS3 pin that it could usefully connect to.
It looks like the selected frequency can be tweaked via I2C, so it might be possible control it using something like setfsb, cpufsb, viafsb if the code for that chip has been written.

Today I recheck it with P3 1GHz (133x7.5) and found
All off - is a Auto mode
SW1 - on, SW2-SW4 - off - is 124MHz
SW1 - on, SW2-3 - off, SW4 - on - don’t start???
Ate there any ideas?

Babasha wrote on 2022-07-06, 18:09:

Today I recheck it with P3 1GHz (133x7.5) and found All off - is a Auto mode SW1 - on, SW2-SW4 - off - is 124MHz SW1 - on, SW2 […]
Show full quote

Today I recheck it with P3 1GHz (133x7.5) and found
All off - is a Auto mode
SW1 - on, SW2-SW4 - off - is 124MHz
SW1 - on, SW2-3 - off, SW4 - on - don’t start???
Ate there any ideas?

Maybe SW4 is connected then, to the FS3 in that datasheet (page 12). In that table a '0' is 'on' and '1' is 'off', and FS0=SW1, FS1=SW2, FS2=SW3 FS3=SW4.

So SW4..1=off,off,off,on is the same as FS3..0=1110, which from the table gives FSB@124MHz, PCI@31MHz
SW4..1=on,off,off,on is the same as FS3..0=0110, which should be FSB@68MHz, PCI@34MHz.

Maybe the FSB clock is too slow for the P3? If you want to clock it at 133MHz then try setting SW4..1 to all on.

I will recheck it tomorrow with my P3. All on is 80MHz with Cel900…

My test rig 😀

Yeah, it's odd. In your first table then SW4 doesn't seem to do anything. But then with the P3 it does, and the 124MHz fits with the datasheet. May just need a bit more experimenting.

Switches test with PIII 1GHz Coppermine

Added to the TRW database:
https://theretroweb.com/motherboards/s/abit-ab-vh20