<Hi, i just bought an Epox 8KTA2 mobo for my Duron 800 and there's a jumper setting that I don't understand. The setting is for "CPU Vio Voltage", which I assume means input/output voltage.>
Quite right, CPUs have two operating voltages:
The internal voltage (core voltage) which is the one everybody talks about when they're overclocking witch commonly ranges from 1.1V (in some motorola comms chips I've worked with MPC82x0 etc.) to 2.5V for ultraSPARCS (I might be wrong with this value, please hold back those flames). Athlons and the like use voltages in the middle of this range. The core vlotage is fairly small 'cos it only needs to get over very small distances on the silicon (it also comes down to power dissipation, but lets not cover that!). You don't need a big voltage to drive signals high fast when there's only a short distance to travel. This is why you sometimes need to increase the core voltage when overclocking, at higher clock rates the lines in the core don't get driven high quickly enough to stablise at a "high" logic before the next clock pulse. Increasing the voltage allows the lines' voltage to rise beyond the barrier between high and low faster.
The Vio is the voltage for the chip's Input and output to memory etc. Because the lines between the processor and northbridge are much longer than the ones on chip (measured in millimetres rather than microns!) the low voltage used in the core just isn't stable enough over these long distances. It comes down to a combination of getting a clear differenciation between high and low logic values, the inherent capacitance and inductance of the lines, and electromagnetic interference. Most chips noadays use 3.3V-3.9V or 4.5V-5.5V for Vio (once again these are values from the deap recesses of my memory 'cos I can't be bothered searching out any of the spec. sheets I have hidden away).
<This setting is not the same as the core voltage, which I know should be 1.6v,and this is set by DIP switches (or auto). The jumpers have settings for
3.4v-3.75v in incriments of .5v. The mobo came with it set to 3.4v for safety reasons I assume.
Anyone know what I should set this to? I scoured AMD's web site and couldn't find anything to help me. I downloaded a bunch of .pdf docs from Epox and AMD and searched for "voltage", but nothing relevant came up.>
I'd advise leaving it as it is or setting to "auto".
HTH
Sorry about the length, I get carried away a little sometimes!
Fat Chucky
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