Getting to grips with DDR2 technology.

Inquisitor M · 15 Jul 2009 at 14:36

So, sorted out my chronically overheating CPU issue and now turning my attention to RAM. Still not overclocking much at this stage until I'm totally up to speed on my info.

So, understanding DDR2, just want you guys to make sure I have my facts right and steer me back on course where I am wrong.

At the most basic, my motherboard (Foxconn G33M) supports DDR2, thus it will only run DD2 memory. Period.

The 'codname' (PC-5300 etc.) of DDR ram is the difference in speed capability and not any difference in actual technology. For example my M/B only supports 800Mhz DDR2, but I can safely fit 1066Mhz DDR2 for the purposes of overclocking.

My current RAM is 333Mhz (PC-5300), but has been running as 400Mhz since day 1 and has been perfectly stabe, however it left almost no tolerance for overclocking (abut 850FSB was the stable limit). Since I can't unlink the FSB and memory clock on the motherboard, dropping the BIOS setting for the memory from 800 to 667 and then boosting the FSB up so that the memory clock is back to 800 again (yes I know it's 400x2) should be exactly as stable as it was before, yes?

Based on the fact that dropping the memory core to 667 in the BIOS changed the instability threshold from 850 to 1000+FSB, is it reasonable to assume that throwing in actual 800Mhz RAM (or 1066 if the above assumption is correct) will boost me past that limitation?

Cheers for any help.

Scott

PhillyDee · 15 Jul 2009 at 14:49

Yes. 800mhz ram will run at 800mhz (400x2). 1066mhz ram is guaranteed to run at 1066mhz (533x2).

Except if your current ram is PC-5300 then its actually DDR. DDR2 is PC2-5300. I assume thats just a typo though!

Inquisitor M · 15 Jul 2009 at 14:57

Yeah, you're right, just a typo, well, technical innaccuracy to be more fair, I'm still learning!

Geez, I remember the good (HA! is if) old days of DX266's and Vesa Local BUS. When men were men and DOS was king! I let myself get intellectually out of shape...

Big.Wayne · 15 Jul 2009 at 14:58

Hey Inquisitor M,

basically you got it right and nice one for getting a good overclock from your old RAM!

As your aware to increase performance on your system you need to deal with a few variables like processor speed, FSB speed and memory speed, if any one of them variables meets its limit then your stuck.

As regards memory the two main factors for boosting the RAM frequency are having sticks capable of running uBer fast MHz *and* a motherboard with a good Northbridge chipset that features support for DDR2-1066 and DDR2-1200

Your Foxconn G33M uses the Intel® G33 Express Chipset which appears to only offer DDR2 800/667MHz support so you may be out of luck for getting some newer mega fast DDR2 although you can't be 100% sure until you tried (or do a ton of homework/research).

Inquisitor M · 15 Jul 2009 at 15:37

Well my biggest problem seems to be that I can't unhook memory frequency from FSB, and since both CPU and FSB multipliers are both locked (think I remember reading that's common for Intel chips?), I just need the ram to cope a little more so I can push the FSB a little higher.

If I exclude the Northbridge from the equation for a moment, and assume that 400MHz DDR2 would overclock by as much as my 333MHz, then I could theoretically push the FSB to around 1120 with around the same comparative load on the higher specc'd RAM.

That would put the CPU at around 2.6GHz, which is quite enough for me, if the Northbridge cuts me off before that, then faster RAM is irrelevant anyway. So, the question is, in other people's experience, is getting 400MHZ out of 333MHz RAM unexpectedly good? Could I expect to manage something similar with actual 400MHz RAM or should I not be pushing my luck and just buy 533MHz and stop being a cheapskate in case it fries?

What would you EXPECT to be able to overclock the Northbridge my in relative safety?

EDIT: Note my big reservation is that I'm only running WinXP at this time, so 2x2Gb sticks of 1066 is a bit overkill and wasteful for now.

dirtydog · 15 Jul 2009 at 15:40

There should be an option to change the memory divider somewhere in the BIOS settings unless your BIOS is particularly restrictive. You shouldn't have to run at 1:1.

Inquisitor M · 15 Jul 2009 at 15:41

I could be blind..it's sadly common, but I can't find any such thing.

dirtydog · 15 Jul 2009 at 15:46

I'm just looking at your motherboard's manual online - although it isn't very informative.

If the option is there it looks like it will be in the 'Fox Central Control Unit' section somewhere. It would be an odd thing to omit, it's pretty basic functionality.

Inquisitor M · 15 Jul 2009 at 15:54

It's not in that section, all the other overclock options are there, FSB, 667/800 memory select, ram timings selection, no capacity to unlock though.

So like I said I've just dropped it from 800 to 667 for now to aquire headroom. Now to play what RAM to throw in and see where it gets me. The reviews did say it wasn't very strong on overclocking, though considering the FSB some of those reviews managed, the Northbridge should hold up a good long while.

Big.Wayne · 15 Jul 2009 at 16:32

Inquisitor M said:
Well my biggest problem seems to be that I can't unhook memory frequency from FSB

Inquisitor M said:
the other overclock options are there, FSB, 667/800 memory select, ram timings selection, no capacity to unlock though.

I've just dropped it from 800 to 667 for now to aquire headroom

Hery Inquisitor M,

it seems you have solved your "biggest problem" by changing your memory from asynchronous to synchronous meaning that your memory is now running the same base frequency as your FSB (1:1).

This idea you have of "Unlocking" memory is something I'm not familiar with, I think maybe you are getting confused with all the different jargon.

Here's a handy chart showing basically how the memory dividers work, they just match a Predefined FSB to one of several Predefined memory standards . . .

What processor are you using?

Inquisitor M · 15 Jul 2009 at 16:49

Ahh, that makes sense, yes I was confused over the idea of 'unlocking', I had assumed it ment completely detatchig the memory frequency from the FSB. (though I'm totally unsurprised that isn't what it means)

I have an E2160, so 200MHz processor default FSB, overclocked to 250 (1000MHz FSB) so far and perfectly stable using 5:3 memory frequency ratio (416MHz). One of the chips will go a bit further, the other won't, so its staying exactly like this untilI get new DIMMs.

Nice chart Big Waybe

Big.Wayne · 15 Jul 2009 at 17:04

I have an INTEL® E5200 processor that has a standard 200MHz-FSB (or 800MHz System Bus), the max speed of the Memory for that chip non overclocked is 400MHz (or DDR2-800) using the 2:1 asynchronous Memory divider (i.e the base Memory clock will be twice as fast as the base FSB).

If you can overclock a chip so it's using a 266MHz FSB then it's possible to make use of 533MHz Rams (DDR2-1066) *if* your motherboard can support it.

The chip you are using may well not like running on a very high FSB so you have a few unknown variables to deal with (can chip hack it, can motherboard hack it etc).

BTW the chart isn't mine but lifted from a nice anadtech article

Further Reading:

Why we were wrong about the Intel X48
Skim through and learn more about tRD and Memory Ratios

Guide to Determining Optimum Overclocked System Performance Points
View and download TTR Overclocking Guide.xls at the bottom of the page

Inquisitor M · 15 Jul 2009 at 17:24

Well the E2160 itself has been reported to be happy as a clam at up to around 3GHz by multiple sources, so I'm less fussed about that, and more about how the MB itself is handling it, or more specifically, the RAM side of it. Still, I know where I am going now thanks to you guys, experiemntation is the next step! MAWHAHAH!

That and buying better RAM...