Explain VTT clocking to me

HangTime

HangTime

HangTime

Man of Honour
Joined
25 Oct 2002
Posts
31,893
Location
Hampshire
I've had my current setup (i5-750, MSI P55 GD65) for a while now. I had settled on 4.095ghz (21*197) but with a new graphics card on the way I thought it time to start pushing the envelope a bit.

Anyway my target to start with is 21*200 = 4.2ghz. However it seems that to get this stable I (probably?) have to push VTT up quite high (around 1.39v). The board seems to think over 1.35v is risky as it makes the number go red, this is why previously I've held back and not got up to 4.2ghz. It seems being more aggressive with VTT is potentially paying dividends, and reading around overclocking articles it seems using up to 1.4v isn't that uncommon.

However whenever I look on the forums people seem to be running lower VTT than me (under 1.35v). So really I could do with some input on this... should it be having much influence on my overclocking? What are the risks?
 
1.254v VTT for my i5 750 at 4GHz. It's perfectly stable at that, but to go to 4.1 or above requires oodles of VTT so I've decided it's not worth it for the sake of chip longevity.

I think Intel revised upwards the safe VTT on Nehalem chips after they were released, which accounts for the red numbers in bios sooner than you'd expect. OC Genie on my board sets VTT to 1.35 which comes up red, but is apparently safe.
 
Played with this a bit more today and it seems that either I'm close to the limit or am getting very severe diminishing returns. Even just an extra 2mhz bus speed isn't stable even if I push VTT up to 1.404 and give the vcore a bit more juice as well.

So now I have a dillemna, with three main options:

1) Drop back to 197 bus speed and ease back the voltages a lot
2) Settle for 200 bus speed with moderately high voltages
3) Go overboard and really start cranking things up i.e. suicide run whacking 1.45v through vcore and vtt and just see if that gives me anything extra.

Option 2 seems best but the overclocker in me that grew up in the days of much more limited voltages/bus speeds is tempted to explore the options that are there even if it could be dangerous.
 
Some decisions you have to make for yourself :D

If you can afford to risk frying your chip then option 3 and have fun. If you need it to keep working then option 2 is more sensible.

You sound more liike an option 3 kind of person though :)
 
My VTT is set to 1.34v and cpu to 1.34v for 200x21 and shes prime stable for 8hours. Although the cpu goes down to 1.3v under load.

What voltage is your memory at? Doesn't it have to be within 0.5v of your vtt iirc?
 
You must log in or register to reply here.
Back
Top Bottom