hardware fixes

motherboard bus speed

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Motherboards with the PLL chip PLL52C59-14 can run at up to 75 MHz. They also support the 'turbo frequency' feature, which increases the bus speed by 2.5% (officially approved by Intel's CPU specifications).

For 75 MHz
Pin 8 via 2.2 k Ohm to 0 V ('0 V' means 'ground' and NOT 'disconnected'!)
Pin 12 via 10 k Ohm to 5 V
Pin 13 via 10 k Ohm to 5 V

For 68 MHz
('turbo frequency' of 66 MHz)
Pin 8 via 2.2 k Ohm to 0 V
Pin 12 via 10 k Ohm to 0 V
Pin 13 via 10 k Ohm to 5 V

For 61.5 MHz ('turbo frequency' of 60 MHz)
Pin 8 via 2.2 k Ohm to 0 V
Pin 12 via 10 k Ohm to 5 V
Pin 13 via 10 k Ohm to 0 V

(Measured on the Abit boards IT5H, IT5V, PR5, which all use the PLL52C59-14.)

Motherboards with the PLL chip PLL52C61-01 can run at up to 83 MHz. They also theoretically support the 'turbo frequency'. There is obviously a way of configuring this chip, so that it would run at 61.5 MHz instead of 83 MHz.

For 83 MHz (sometimes 61.5 MHz, depends on motherboard implementation)
Pin 5 via 10 k Ohm to 0 V ('0 V' means 'ground' and NOT 'disconnected'!)
Pin 12 via 10 k Ohm to 5 V
Pin 13 via 10 k Ohm to 5 V

For 75 MHz
Pin 5 via 10 k Ohm to 5 V
Pin 12 via 10 k Ohm to 0 V
Pin 13 via 10 k Ohm to 5 V

For 68 MHz (the 'turbo frequency' of 66 MHz)
Pin 5 via 10 k Ohm to 5 V
Pin 12 via 10 k Ohm to 5 V
Pin 13 via 10 k Ohm to 5 V

(I have measured this on the Asus P/I-P55T2P4 rev. 3 and the FIC PA-2006 board. The FKI SL586VT II, Magic Pro MP-586VIP and ABit PR5 board also use this chip, but you can't get to 83 MHz. Instead you get the pathetic speed of 61.5 MHz.)

In terms of jumpers, this means that you will have to find out which of the three jumpers is connected to the particular pins. It's circuited via the pull up/down resistor of 10 k Ohm. In case you only have jumpers with ON/OFF positions instead of 1-2/2-3 positions, the ON condition is the condition for 0 V, and the OFF or open condition is for 5 V.