5. Go find the bios area that allows for Core Disabling. Disable one module "of" two cores. Then set multiplier to equal 200 times X (multiplier) of the FX-6300. The theory is that with two of eight cores disabled you have 6 cores in use and with the multiplier set to give the speed of the FX-6300 >> well there you have the FX-6300.
Well it does not work quite that way. It sounds awesome in theory but the less expensive motherboards do not allow for manual setting of multiplier and STILL have turbocore work. If TurboCore does not work then you have all 6 cores on at all times and that is hotter than an FX-8320 left to run as AMD designed it to run.
As for what voltage to use in an underclocked condittion, that is the same trial and error procedure as if we were trying to 'overspeed' the processor. Each cpu is different. No one is ever sure what cpu voltage will be actually needed until they begin an overclock and the same is true if you are trying to undervolt. You will have to try and apply a lower votlage and test for stability the same as if adding voltage to compensate for increased cpu speed.
In the end because of how various brands and models of board operate, slowing the standard default speeds of FX-8320 to match an FX-6300 by multiplier manipulation, may make TurboCore un-workable. That will add heat since the cores will all be on all the time. YOU will have to test that on your own board. How much Vcore, 'less' than standard voltage can allow for stable operation is a variable that each system will have to have checked at the local level by each user.
If you want FX-6300 cpu characteristics, you might actually do better to sell the FX-8320 and buy an FX-6300 and try to undervolt it. The real situation with AMD cpus is that of any FX processor built or manufactured in the PileDriver series likely has been made with a default cpu voltage requirement of from 1.25V at stock speed to as high as 1.525V for some of the newer FX-9xxx cpus. That default cpu voltage is programmed into the cpu and the cpu hands off that "required" voltage number to the board at booting time. That wide variation in voltages is on a per cpu basis. What the default cpu voltage is for a cpu is not known by us. Each cpu bullt over time may have a widely varying default cpu voltage and that is where the trial and eror begins for each user. Whether he is going to overclock and need to increase cpu voltage or in the reverse methodology of trying to undervolt the cpu.
I don't doubt your project idea cannot be accomplished to some extent, but there is certainly no do A and do B and C will be the result.
RGone...