Everything you want to know about overclocking with a Gigabyte motherboard

Everything you want to know about overclocking with a Gigabyte P45 motherboard

Here's my attempt to give back to the community. I learned a lot here for my first OC and didn't even need to ask anything. Help me compile as much info as we can here.

I'm new to overclocking so I'm both learning what options are available and how this Award BIOS presents them compared to AMI (or whatever Asus boards use). Please chime in when you see something missing or incorrect. I appreciate all the input I can get!

My system:
Motherboard: Gigabyte EP45-DS3R, F8a BIOS
CPU: Intel Core 2 Q9450
Memory: Mushkin Ascent PC2-8500, 2x2GB
rest in my sig...

Last update: July 30, 2008, 8:55 PM

I'll cite settings for 3 clock speeds, when the settings differ:
1) 8x 440 = 3.52 GHz, prime stable for 9d18h45m
2) 8x 485 = 3.88 GHz, unlikely to be stable, but I'm getting close, 25 mins so far
3) 8x 500 = 4.0 GHz, my personal best, completely unstable, prime95 causes an instant BSOD

All these BIOS settings are in M.I.T. - Motherboard Intelligent Tweaker.

CPU Clock Ratio:
Stock: 8x (for the Q9450)
Mine: 8x
This multiplied by your clock speed gives your final cpu clock. Range is 6-8 for the Q9450. Mine is 8x... isn't everyone's q9450 at 8x?

Clock Chip Control

>>> Standard Clock Control

CPU Host Frequency (FSB clock):
Stock: 333MHz (for the Q9450)
Mine(1): 440MHz
Mine(2): 485MHz
Mine(3): 500MHz
No explanation necessary, is there? Push her as high as you can, especially if you only have an 8x multiplier.

>>> Advanced Clock Control

CPU Clock skew:
Stock: 0ps
Mine(1,2,3): 150ps
This and MCH clock skew are like voodoo. The benefits are clear but the only way to find out if it helps is trial & error. I lucked out and found that 100ps CPU skew & 250ps MCH skew let me boot at FSB clock speeds I couldn't even POST at, such as 475MHz. At lower clocks they help stabilize things too. I can get higher clocks with all stock voltage. Then with some trial & error going for 500 I found 150 was a bit better. Make sure you read MCH skew for more info (next, just keep reading).

MCH Clock skew:
Stock: 0ps
Mine(1,2,3): 250ps
See CPU Clock skew above for basics. The trick to tuning these is that they go together, so you should make a grid with timings your board allows and then start trying random combos till something helps at frequencies you can't even POST at. Then when you hit something keep tuning them trying all the near combos. Tedious, but essential.

DRAM Performance Control

Performance Enhance:
Stock: Turbo
Mine: Standard
I don't know what this changes, haven't bothered testing it.

(G)MCH Frequency Latch:
Stock: Auto
Mine(1,2,3): 333MHz
This would be your FSB strap in Asus/AMI lingo. At low fsb speeds I can set this to 400 or 333, but at higher speeds I have to keep it at 333 and keep a 1:1 ratio (see below).

System Memory Multiplier:
Stock: Auto
Mine(1): 2.40B
Mine(2,3): 2.00B
I believe Asus boards call this the divider. This changes your FSB strap according to the letter suffix. To run my memory & cpu in sync I have to keep this at 2.00x, and specifically 2.00B at higher clocks. The letter suffix is explained in the BIOS.

At 5:6, 1056MHz, latch is 333MHz (2.40B).
memory clock = latch * FSB = 2.4 * 440 = 1056MHz
multiplier (or divider) = FSB / RAM = 440 / 528 = 5/6

DRAM Timing Selectable:
Stock: Auto
Mine: Manual
I have these at 5-5-5-15, I'm leaving the fine-tuning till I find my max stable speed.

Advanced Timing Control

Not yet.... There will be more here later, as the timing options are rather cryptic and warrant explanations & comparisons to Asus/AMI terminology. I only know what a few of them really do so far.


Voltage

CPU Vcore:
Stock: 1.25v
Mine(1): 1.35v
Mine(2): 1.45v
Mine(3): 1.475v
Voltage to your cpu, but we all knew that one. Defaults to ~ 1.25v for 45nm cpus. Max. recommended by Intel is 1.38v for the Q9450, I have seen people report going as high as 1.5v for suicide runs. My board has a vdrop of ~ 0.05 above 1.3, and ~ 0.01-0.02 below 1.25 or so. vdroop is 0.05-0.07.

I don't want to be the one to find out that 1.45v (CPU-Z reading, idle) kills your CPU in 3 months, so even if I stabilize 4GHz I don't know if I'll run that high normally. 1.4 already sounds high to me, so that's my absolute limit for every day operation (for now anyway! )

1.35 BIOS results in 1.248 load and 1.312 idle.

CPU Termination:
Stock: 1.2v
Mine(1): 1.24v
Mine(2): 1.32v
Mine(3): 1.34v
This is known as CPU VTT on Asus boards. Turning this up helped at high frequencies but I found that after setting the clock skews I could turn this down to the stock setting and still get >400 mhz. I read that this is key to OCing quads, so I'll experiment with it when I try to break 450.

CPU PLL:
Stock: 1.5v
Mine(1): 1.57v
Mine(2): 1.61v
Mine(3): 1.61v
When increasing vcore + other settings I increase this too. I am uncertain of what it does, and I have seen recommendations that this stay below 1.55v. This board goes in weird increments, 1.5 -> 1.57 -> 1.59 -> 1.61.

CPU Reference:
Stock: 0.76v
Mine: 0.76v
I gather that reference voltages are used to determine whether a signal is high/low. At higher voltages it may be wise to increase this slightly, but I haven't touched it yet. I believe I read that this should be 65-70% of vcore.


MCH Core:
Stock: 1.1v
Mine(1): 1.2v
Mine(2): 1.34v
Mine(3): 1.36v
Voltage to your NB (north bridge). MCH stands for Memory Controller Hub. I don't think I could go past 1.4. It might be safe but I haven't any info on how much it can take.

MCH reference:
Stock: 0.9v
Mine: 0.9v
The same as the other ref. voltages but for your NB.

MCH DRAM/reference:
Stock: 0.76v
Mine: 0.76v
See other reference voltages above.

ICH I/O:
Stock: 1.5v
Mine: 1.5v
Voltage for your SB (south bridge). ICH stands for I/O Controller Hub.


DRAM Voltage:
Stock: 2.0-2.1v
Mine: 2.06v
Another no brainer, volts to your memory. Oddly most boards give your memory a bit more than you specify here. I get 2.06-2.08.

DRAM Termination
Stock: 0.9v
Mine: 0.9v
This is the voltage that terminates signals to your memory.

Channel A/B Reference:
Stock: 0.9v
Mine: 0.9v
The same as CPU reference but for memory.

If you want me to list a BIOS setting I skipped over just let me know.

I like where you're going with this and I think it will become inherently useful. The EP45-DS3R is a great P45 board and I'm sure many will have questions for optimal settings. I can't contribute as I don't have one, but thanks for taking the time to do this. Many will be appreciative.

-Collin-

Thanks ninjaZX6R, it is a good board I am digging it so far except for the frackin vdroop. Perfectly happy with it's clock speed as I haven't even dropped the cpu's multi to really push it yet, and I got to 475. Until my E8400 arrives I won't be able to max it out.

So I went and upped the vcore a little as nothing else was helping. I'm still only at 1.2v load (BIOS 1.29v) but with this shuriken cooler I'm at 85C in the afternoon & 75C at night when running prime95. After a few hours of the blend test I got a rounding error. I'm almost positive I don't need more vcore so I increased vdimm to 2.0v. Only been priming for 40 mins so we'll find out if it's stable tomorrow. ... I really want to get this thing stable past 3.6.

samsonJS said:

Thanks ninjaZX6R, it is a good board I am digging it so far except for the frackin vdroop. Perfectly happy with it's clock speed as I haven't even dropped the cpu's multi to really push it yet, and I got to 475. Until my E8400 arrives I won't be able to max it out.

So I went and upped the vcore a little as nothing else was helping. I'm still only at 1.2v load (BIOS 1.29v) but with this shuriken cooler I'm at 85C in the afternoon & 75C at night when running prime95. After a few hours of the blend test I got a rounding error. I'm almost positive I don't need more vcore so I increased vdimm to 2.0v. Only been priming for 40 mins so we'll find out if it's stable tomorrow. ... I really want to get this thing stable past 3.6.

Click to expand...

Same here, I have the EP45-DS3R & the V Droop is bad. Any other P35 board I had my E8400 would do up to 4.2ghz @ 1.35 vcore, but with this board set 1.35 or 1.38 in bios means 1.296 at mutli meter or even reading it in CPU-z. I can barely get 400 fsb @3.6ghz stable. I am afraid these P45 chipset boards are gonna be a mother to get a handle on. From what I have been reading the CPU MCH Skew setting are it.

SlackAdjuster

I have the same board and an e8400 and yes, the vdroop is less than stellar... I am currently running at 3.8GHz with 1.360v reported in cpu-z which is like 1.418v set in the BIOS. So far I am 2+ hours stable in ORTHOS... I'd like to hit 4.0 but i don't think i can reach that. I have not touched MCH or CPU skew yet and my ram timings are set to run at recommended 5 5 5 18 with 2.1 v DRAM voltage.

I have a question about SMM (System Memory Multiplier). I was wondering if i should use 2.00D or B for ddr2 800 PC26400 ram? I figured it would be 2.00B however when I use this and set the latch as 333 it barely posts at higher 3 GHz clocks. Right now i have the latch frequency set to auto and the system memory multiplier set as 2.00D, pretty stable for 3.8GHz..

slackadjuster: i agree this board can be fussy but i only run into problems at very high speeds (> 450-475) so it's not that bad really. i'm only pushing these high speeds for fun not for an every day clock so a bit of tweaking doesn't put me off that much. my e8400 sucks for OCing judging from the results I've seen. Should have held out for an E0 stepping.

kawai: I'll have to try 400mhz on my e8400 as you're the 2nd person to report higher clocks at that latch. i'm really pushing the limits of my cpu right now trying to stabilize 4ghz with 1.472-1.488v load under prime95. clock skews play a role with this cpu too but not as much as with my q9450.

my e8400 clock skews for the ep45-ds3r (fav. to least fav, no conclusive evidence for a best one yet):
(cpu, mch)
(250, 50)
(200, 200)
(200, 100)

edit: If I want to boot my e8400 at fsb 475 or higher setting the right clock skews is mandatory.