Limiting ram speed on a P5Q Pro

titaniumx3 · 23 Dec 2008 at 13:50

Hi,

I currently have a P5Q Pro + Q9550 pro at 3.4ghz using DDR2-800 ram.

I'm trying to get above that, but as soon as I do, I quickly get errors in prime95.

Looking at the bios I think the problem stems from my ram, which seems to overclock automatically with the fsb. For example, if I set fsb at 450mhz, ram also overclocks to 450mhz. Also in the dram frequency options (under AI tweaker menu), there is no setting to go below the fsb speed, e.g. at 450mhz fsb, the lowest dram frequency is DDR-900.

I'm thinking there has to be some sort of fsb:ram divider, but I can't find it. Any ideas?

Some help would be greatly appreciated!

Guzzidom · 23 Dec 2008 at 14:08

Set FSB strap to 333 (which is quad pumped so it will make the system bus 1333mhz and your ram 666mhz at stock) then you should be able to bump the fsb back up to 400mhz which in turn will be overclocking the bus speed to 1600mhz and your cpu by the same margin (to 3.4ghz).

Now you already know your ram will go to nearly 450mhz so that won't be the bottleneck for further efforts, the CPU volts might need a minor lift to go further and the Northbridge might need to have a little voltage lift to get beyond 1600mhz FSB, the P5Q board can handle 1900-2000mhz with these adjustments as far as other peoples results go though mine is at a mere 1800mhz for temp reasons.

titaniumx3 · 23 Dec 2008 at 15:20

Guzzidom said:
Now you already know your ram will go to nearly 450mhz so that won't be the bottleneck for further efforts

Thats the thing, the system boots at 450mhz, but I think it's the ram thats giving me those prime95 errors. I would like fsb to be at 450mhz, but the ram at 400mhz (stock).

I tried upping the cpu voltage to 1.3v, but I still got errors almost immediately, with the cpu barely heating up. That said, I haven't tried increasing the northbridge voltage yet.

G_Wizz · 23 Dec 2008 at 15:35

You can't run the ram at less than the FSB, only the same or higher.

Sweeney · 23 Dec 2008 at 15:42

What RAM is it?

Relax the timings on it and try, see what voltage limitations are for them and up the voltage a little. Generally most top brand 6400 (800MHz) ram will run above spec sometimes need a bit of extra help to though

titaniumx3 · 23 Dec 2008 at 16:12

Sweeney said:
What RAM is it?

Relax the timings on it and try, see what voltage limitations are for them and up the voltage a little. Generally most top brand 6400 (800MHz) ram will run above spec sometimes need a bit of extra help to though

The ram is either this:

http://www.ocztechnology.com/products/memory/ocz_ddr2_pc2_6400_vista_performance_platinum_dual_channel

or this:

http://www.ocztechnology.com/products/memory/ocz_ddr2_pc2_6400_vista_performance_platinum_4gb_dual_channel

I think the default voltage is 1.8v. Would it be safe to increase this?

!TIMMY! · 23 Dec 2008 at 16:32

Yes, both the ram u linked to say:

2.2V EVP**

**OCZ EVP (Extended Voltage Protection) is a feature that allows performance enthusiasts to use a VDIMM of 2.1V without invalidating their OCZ Lifetime Warranty.

From the OCZ site.

So you can go up to 2.1v and still have warranty.

Guzzidom · 23 Dec 2008 at 18:00

titaniumx3 said:
Thats the thing, the system boots at 450mhz, but I think it's the ram thats giving me those prime95 errors. I would like fsb to be at 450mhz, but the ram at 400mhz (stock).
.

That's what I'm trying to tell you to do lol.
Set your "strap" to 333 mhz and then gradually bump up your fsb until the ram is at 400mhz, you will then find your FSB to be at 1600mhz (800mhz x 2) and your CPU will be at at 3.4. After that it's gently gently a few meg at a time until you reach the limits of your chip (somewhere between 3.6 and 3.9 on air it seems) .
Your entire problem is the 400mhz strap that I'm guessing, you've set, this natively sets your system bus to 1600mhz, at a 450mhz overclock your system bus is twanging away at 1800mhz and your ram is starting to run out of headroom too.
With a few voltage changes and loosening the ram timings you could probably get it straight, but you are way better off starting the proceedings at 333mhz if you want to see what your CPU is made of.

titaniumx3 · 23 Dec 2008 at 19:21

Guzzidom said:
That's what I'm trying to tell you to do lol.
Set your "strap" to 333 mhz and then gradually bump up your fsb until the ram is at 400mhz, you will then find your FSB to be at 1600mhz (800mhz x 2) and your CPU will be at at 3.4. After that it's gently gently a few meg at a time until you reach the limits of your chip (somewhere between 3.6 and 3.9 on air it seems) .
Your entire problem is the 400mhz strap that I'm guessing, you've set, this natively sets your system bus to 1600mhz, at a 450mhz overclock your system bus is twanging away at 1800mhz and your ram is starting to run out of headroom too.
With a few voltage changes and loosening the ram timings you could probably get it straight, but you are way better off starting the proceedings at 333mhz if you want to see what your CPU is made of.

How will the fsb strap affect the ram speed? Does it keep it locked? In the bios the fsb strap is called "fsb strap to north bridge" which I currently have set to auto.

In any case, am I right in saying that the ram can't be run at a lower speed than the fsb?

Sweeney · 23 Dec 2008 at 20:25

afaik, the p45 can't run the ram slower than fsb only nforce can...? The fsb strap is to keep the ratio 1:1 or to set the ram faster than fsb, i.e. fsb of 333 but running ram at 400.

I suggest upping the timings of your ram to 5-5-5-18 and the volts to 2.0, then see how that fairs. Running the fsb at 450 = 900MHz which is an overclock of 100MHz on the ram which i'd expect OCZ to take in its stride however mine didn't

Also, you might need to up various other voltages to keep things stable as ram could only just be playing a part in the issue

Guzzidom · 23 Dec 2008 at 20:54

titaniumx3 said:
How will the fsb strap affect the ram speed? Does it keep it locked? In the bios the fsb strap is called "fsb strap to north bridge" which I currently have set to auto.

In any case, am I right in saying that the ram can't be run at a lower speed than the fsb?

Aaah, I'm at home now and can see I was misreading this, change the "Dram Frequency" to the lower value shown in the drop down box...job done.

You will still want to lock the FSB strap to Northbidge to 333mhz though, just so you know what the bugger is doing if nothing else, otherwise it's a variable you don't need.