Overcloacking Core 2 Duo e7500 FAIL
I recently tried to OC my CPU and messed around with the multipliers and got the number of GHz i wanted which was 3.0. When restarting my computer the number didn't take effect but it was saved in the bios. A friend told me that maybe my motherboard can't stand OC. My motherboard is a GIGABYTE GA-EP43-UD3L LGA 775 is old, is still DDR2 but it does the job. My CPU is a Intel Core 2 Duo e7500 2.93GHz. I just wanted to have the 3.0Ghz just to test the OC.
Check to see that speedstep wasn't in effect. This will underclock your cpu until you put a load on it, then it will run at its full speed. Run a program like CPU-ID and watch the multiplier as you put a load on the cpu.
That chip has a pretty high multiplier so it should be pretty easy to get a moderate overclock with it.
Your chip has a multiplier of 11. For overclocking you normally do not change the multiplier, leave it at 11.
Let's say you wanted to run your chip at 3.3GHz.
1. Set the main bus frequency to 300MHz. My BIOS calls this "CPU Host Frequency".
2. Set the Ram to run at its lowest frequency, depending on your motherboard BIOS this might say 1:1 or 2:1. As you change this setting you should be able to see what ram speed it is going to run at, just get this ram speed to its lowest for this stage of overclocking. My BIOS calls this "System Memory Multiplier". The best you can do on this is probably a setting of 2.0A or 2.0B.
3. You might need to set your PCI bus to 100MHz. (PCI Express Frequency).
These are all of the settings that you have to change. It should boot and run fine with these settings. You should check with something like coretemp to see that the cpu isn't getting too hot when you load it.
There are LOTS of overclocking guides on the net that will tell you all of this stuff. I have a very similar motherboard in my machine, and EP45-UD3R (I think), along with an E8500 CPU, and I am running it right now at 3.8GHz.
This article is somewhat close to what you are doing, with a similar motherboard:
I have an E7500 running at 4.1 GHz in a Gigabyte EP35-DS3P motherboard.
This should be your first stop.
Core2 Overclocking Guide (generic guide)
Shadow's Gigabyte motherboard OC guide:
It's for an EP35-DS3L but all the Gigabyte Core2 BIOS's are similar.
Go through the guides. Then take your core voltage off Auto and set your memory voltage to factory recommended values. Change the System Memory Multiplier from AUTO to 2.00. Then when you increase the FSB, the memory clock will rise in in proportion with it. At an FSB of 266 MHz, your memory clock should be at 533 MHz.
Download CPU-Z to check your FSB:RAM ratio. It should be a 1:1 ratio.
cadder is right. You want to set the System Memory Multiplier to 2.0. Don't bother with overclocking the RAM. The minimal increase in performance is not worth the decrease in stability.
You can run the memory at up to 2.2 volts. Do not exceed 1.50 volts CPU vcore. Keep your load temps under 70 C.
The Wolfdale cores are pretty efficient. They do not need top grade cooling like the quads do.
I have 4 OC'ed Core2 systems:
GA-EP45-UD3P | Q9550 OC'd to 3.6 GHz (425 MHz X 8.5) C3 stepping
GA-EP45-UD3L | Q6600 OC'd to 3.6 GHz (400 MHz X 9)
GA-EP35-DS3P | E7500 OC'd to 4.1 GHz (373 MHz X 11)
GA-G41M-ES2L | E6500 OC'd to 3.87 GHz (352 MHz X 11) FSB limited by G41
All are 24 hour Prime 95 stable, running at 1:1 with SpeedStep enabled.
My gaming system (the Q9550) has been good enough that I have been able to skip two CPU generations and wait for Ivy Bridge.
Overclocking since 1978 - Z80 (TRS-80) from 1.77 MHz to 2.01 MHz