I don't know, but it's highly unlikely to work optimally with the K6-3. Core voltage adjustment circuit. This resistor network is used to adjust the core voltage output as shown below.
All values approximate.
So with no jumper inserted the lowest voltage available is determined by R43 which is a surface mount component, it is this component that needs to be removed from the circuit and replaced with a different value to get core voltages lower than 2.5V. Testing. I desoldered R43 and removed it to allow calibration. Onto the exposed solder pads I soldered a pair of wires and a 4.7Kohm resistor in series with a 10Kohm variable resistor. The lowest voltage that I was able to reach consistently was 2.28V, by increasing the resistance to try and get lower than this the Vcore voltage will drop to less than 1.0V - almost certainly due to the components or design of the other parts of the voltage regulation circuit. These are the results I obtained.