Can a CPU limit selectable voltages?

[Rayce185]

So in my pursuit to find out why I can#t set the VTT on my XFX 780i over 1.4V (highest available), I was told by tech support that "if the option is not available then this voltage is not supported on this CPU / board configuration".

This is new to me.

I have tried both my Q9550 and a E5200 on this mainboard, and both show a max FSB voltage of 1.4V. Of course it may be a coincidence, but I strongly disbelieve that the CPU alters the BIOS' settings to disable the use of higher voltages. I mean I also have the ability to set the Vcore to 1.8V, so it's not like capping at 1.4V (if that's the case) is protecting the system from overvoltage.


What is your take on this?

[LennyRhys]

Sounds like the guy is just telling you fairytales. My first suggestion would be a BIOS flash since it's possible that an earlier BIOS will have more voltage options.

Other than that I have no idea - 780i is the same as a 680i with an extra chip in the mix, and my 680i board had 1.5 VTT also, with a Q6600 and E8500.

[Rayce185]

Thanks for your reply.

I'm a bit wary about previous versions, as I don't know how the CPU support is on them; I cannot find any BIOS changelogs.

[Elloquin]

You will need an older bios and/or try another vendors bios (ex. evga: I know people were flashing the xfx bios on evga boards when they first came out). I know on the evga 780i earlier bios versions let you set 1.5v VTT as a max and it later changed to 1.4v.

[Rayce185]

You will need an older bios and/or try another vendors bios (ex. evga: I know people were flashing the xfx bios on evga boards when they first came out). I know on the evga 780i earlier bios versions let you set 1.5v VTT as a max and it later changed to 1.4v.

AHA!

Here we got it! nVidia (or whoever made the BIOS) lowered the VTT on purpose for the newer version... If this is a known fact for the EVGA BIOS, it will certainly apply to the XFX one too.



Now I just need to know what the changes were (next to this one) between P07 and P08. not that I will have a different drawback when downgrading.



Or: Is there a way to mod a BIOS flash file? I know this is a usual thing done to GFX card BIOS', but what about mobos?

[Elloquin]

You will need to poke around over here http://www.evga.com/forums/tt.asp?forumid=38
It's an older bios that let you set 1.5v VTT somewhere around P04/P05. To answer your other question their are "modded Bios'" but using them depending on your comfort level with flashing bios' is completely up to you. It's usually a fairly straight forward process but be aware that a failed bios flash will "brick" the board rendering it inoperable. Very small chance but it should be mentioned nonetheless. I would try to dig it out for you (the exact Bios #) but I am at work :p: