Gigabyte 990FXA Bios flash to VRM MOS protection issue

Hey steezebe ! You really don't need VRM protection for the CPU you have (PII X4 955BE).
As you know we have 8+2 phase VRM configuration.
I wanted to know the VRM specification of our UD5, hence I looked into the VRM of our UD5. There is "SiC769" written on each VRM.

Here is the PDF describing tech specification:
http://www.vishay.com/docs/64981/sic769cd.pdf

Referring to main article:


This shows each "Sic769" VRM can provide 35 Ampere current. And We have 8 VRMs for our CPU. This means we have total of 280 Ampere current (8 x 35 Ampere) to feed our CPU.

Now heading to your CPU's default current requirement: (Taken from "AMD Power and thermal Data Sheet")


Your Phenom II X4 955 BE requires 110 Ampere max current at default clock. It means this current requirement will be split to our 8 phases.
And Theoretically each phase will deliver 13.75 Ampere (110 Ampere / 8 phase). This shows our VRM can easily run your 955 at default clocks.

But you have overclocked your CPU to 4.2GHz. And we need to find the current requirement at this overclock. Firstly we need to find Power Consumption at load and then we divide this value by the voltage you had applied for 4.2GHz. Then we get current requirement of this overclock (Ampere = Watts / Volts ).


There is a formula to calculate dynamic CPU power consumption:

Power Consumption(Watts) = [ TDP X {overclocked frequency in MHz / default frequency in MHz} X { Overvoltage / default voltage }^2 ]

I don't know what CPU voltage you have set, and hence I estimate it as 1.525volts with default clock voltage of 1.300volt (just for example)

Now your CPU power consumption at 4.2GHz with full load is:
[ 125 X { 4200 / 3200 } X { 1.525 / 1.300 }^2 ] = 225.76 Watts

Now we divide this by 1.525 volts
225.76 Watts / 1.525 volts = 148 Ampere.
This means 148 Amperes / 8 phase = 18.5 Ampere per phase or VRM.

As you can see each phase is easily capable to provide 35 Ampere current. But your overclock needs only 18.5 Ampere per phase.

YOUR MOTHERBOARD VRMS/PHASES ARE ABSOLUTELY SAFE AS THEY ONLY HAVE TO DELIVER 53% CURRENT OF THE TOTAL POWER THEY CAN PROVIDE.

Therefore you don't specifically need to use the BIOS ver. F8 fixing VRM MOS Protection. This type of VRM protection is only for FX 8120 and FX 8150 because some UD3 have died when those extreme power hungry FX 8 core CPU were overclocked to 4.8-5+GHz. You can freely use what best suits to your CPU in terms of overclocking. Even I am using F7 because it suits best for my 1055T at 4.004Ghz (286 x 14). I have tested my CPU at 4.0GHz at 1.456 load voltage for 13 hours in Prime95 without any issue. And of course my CPU at 4.0GHz consumes power exactly as your CPU does at 4.2GHz.

According to what I have experienced (I have burned two MSI 790FX GD70 and one MSI 890FXA GD70 motherboard, all had 4+1 phase) is that chances of VRM failure come into play when they have to deliver 80+% current of the total current they can provide. Because at this state VRM temperature exceeds the safe range (95c - 110c approximate). Therefore we are very very safe. I can guarantee you will never be able to blow up your board's VRM with X6 or X4 CPU with max overclock.

Those fluctuation in readings are wrong. I get those spikes too at high voltage, usually 1.50-1.55volts. They are monitoring application's flaw as sometimes they seems to have trouble reading exact temp, hence they randomly shows wrong reading. As VRM can easily feed the power required by 4.2GHz 955, there will be no throttling even at full load. You can test. Throttling will only happen when your CPU exceed the Critical temperature range (Tctl) which is about 61c. Just let "Thermal Protection" be enabled in BIOS and you'll be ok.

i am running the f10b on my 1055T and it is a poop bios for overclocking..... the F7 was so much better