On 29/11/2011 4:33 PM, Paul wrote:
(1) CPU Over Voltage (aka Vcore)?
"Over Voltage" means being able to offset the VCore voltage,
so it is higher than the range suggested by the CPU manufacturer.
Normally, the VID codes coming from the processor, are range
limited, to suit the CPU manufacturer and the amount of
"field returns" they can expect for "defective processors".
Range limiting VID, is supposed to prevent people from
abusing their processors.
An enthusiast board, can add an analog offset to the
regulator voltage, in an attempt to thwart the
digital (VID value) limitations imposed by the CPU manufacturer.
VCore = [dig VID low .. dig VID high] + analog_offset
VID changes "on the fly", to support EIST or Cool N' Quiet.
So the digital value, doesn't stand still. It changes while
the computer is running, as a function of P-State desired.
Disabling EIST or CNQ, should make VID a constant value.
If your board doesn't support Over Voltage (like my very nice
$65 Asrock motherboard), you can add a resistor or do a "pencil
mod", to do the offsetting yourself. I added 0.1V to VCore,
by adding a resistor to the regulator. The regulator had
a trim point, making the addition of the resistor easy.
All you need for hints, for home hacking, is the regulator
datasheet.
The regulator has an internal check, which will turn off the
regulator if you go too far. The regulator checks for MOSFET
failures, by monitoring the output voltage. If a design tries
to "trim too high", the regulator will assume a MOSFET has
failed short, and will turn off MOSFET drive signals in response.
Or, attempt to clamp the voltage, by turning on all the low side
MOSFETs until something burns or blows. All in the name of
protecting an expensive CPU from damage.
Okay, I have this setting in my BIOS, is the setting a relative number
(i.e. VID + offset = final voltage), or an absolute setting (i.e.
replaces the maximum VID value)?
My processor's VID range is listed as 1.125-1.40V (
http://is.gd/FiNKO6).
But it's maximum power while running at stock frequency is 1.30V. Would
I need to change the CPU overvoltage if I am not planning to go over its
highest range (1.40V), but still need to increase the voltage just for
overclocking (e.g. need to go from 1.30V to 1.325V, or something)?
(2) VDDNB Over Voltage?
AMD processors now, have Integrated Memory Controllers
right on the processor die. A recent change to the CPU
designs, is the move to split plane powering. When you
buy a motherboard with "4+1" phases, the four phases are
for Vcore, while the fifth phase powers VddNB.
I couldn't find any nice pictures, with all the voltage shown,
so this will have to do. There are actually many voltages
in a motherboard design, but I need a nice picture to list
them all.
http://images.ht4u.net/reviews/2011/...sorgung_th.png
Okay, I understand it's the voltage to deliver to the internal memory
controller on the processor, and it's got nothing to do with the old
northbridge chipsets. I suppose I wouldn't have to touch this unless I'm
overclocking the RAM?
(3) Loadline Calibration?
There is a picture of the datasheet specification here. This
shows a loadline graph, and Intel's spec for "acceptable behavior".
So if your VID was putting out a fixed value, this graph
shows how the voltage as measured at the silicon die, changes
as a function of the current drawn by the processor. Processor
current, goes up in proportion to computing load.
http://support.asus.com/Search/KDeta...44C32C8400&t=2
Okay, I assume this is not something that I'd typically need to play
with when overclocking?
Yousuf Khan