CPU Bus speed changing

TobyH · 26 Aug 2011 at 08:59

I'm in the process of starting the overclocking of my system,again, and I was wondering if there are set frequencies that I should use as I increase the values.

The reason for asking is that I had set the value to 233 MHz and then went to 245 MHz, the computer wouldn't start and defaulted back to the 200 MHz standard value. I then tried it at 266 MHz just to see how it worked and it booted up fine.

Is there a reason for this that I've missed? In the guide on here it says increase by 5 MHz each step (yes I've gone a little more than these steps) but that would mean that there's no reason the 245 MHz shouldn't work...

Can someone explain this for me?

ScratchFive · 26 Aug 2011 at 09:57

which platform?

there are generally no set frequencies, however your system may prefer one specific frequency over another, even though the latter is lower, this is however much rarer than if the latter is higher. (in your case it is a relatively large jump for this to be applicable)

edit: it may also be to do with your motherboard stepping up a voltage, if you have the voltages on AUTO.

Jamiman · 26 Aug 2011 at 10:19

take voltages off auto, in case it's jumping it up. Otherwise it might fry your CPU!

CaptainUnlikely · 26 Aug 2011 at 12:27

Commonly known as an "FSB Hole" although FSB is an outdated term if we're talking modern platforms.
Some boards and chips just won't work at some bus speeds, it's fairly common and nothing to worry about.

TobyH · 26 Aug 2011 at 13:54

The platofrm is the follwing:

Gigabyte GA-G31M-ES2 FSB 1333 Mobo

CPU is Pentium D945 dual core 'Presler' 3.4ghz

Kingston 2 x 2gb DDR II Hyper 1600 Ram

The bios does have an o/c mode, but I think from what I've seen of other peoples bios it is a little more limited in what I can change. Voltages have been set to 'Normal' rather than 'Auto' so I'm pretty sure they aren't changing when looking at speedfan screen.

I've left it testing today while I'm at work at 266Mhz with the ram fsb at std setting with std voltages. Will see how it's going. CPU temp is only around the 35'C mark so I'm not too concerned with that at the moment, especially with the massive Noctua heat sink and fans.

TobyH · 26 Aug 2011 at 14:11

Another quick question.

In my bios I have a very limited ram divider (4+, 3.33, 2.66 or Auto), and a mulitplier that goes up to 17. When I'm checking for max CPU clockspeed should I be reducing the multiplier as well as the ram divider or leave it at 17 (which is std)?

Cheers
Toby