Help with 800 to 1066 2

[JSD7878]

Hello,

My problem is this I have an Abit IP35 Pro Motherboard and my memory is currently running at the lower default speed as illustrated by CPUID which showed under the Tab SPD that I was running at 6400 at 400MHZ.

I know that the board can run my new OCZ DDR2 8500 memory at 1066 albeit unofficially according to this link :

http://www.hardwaresecrets.com/article/477

In this link it suggests that they had no problems changing setting in the Bio's (U-guru) to get the memory to run at those speeds, and I am no overlclocker but I wouldn't mind learning how to do this for this specific purpose. Any step by step help would greatly appreciated.

System Specs:
Vista 32bit home prem.
4GB OCZ DDR2 8500
EVGA GTX 8800 768MB
Antec 850W

 

[SkipCox]

Memory:CPU ratio should be 1:1 for optimal performance.

First of all, exactly what processor are you running?





Skip

 

[JSD7878]

Oh Sorry Processor is Intel Core Duo E6850

 

[BadBigBen]

have a read, it explains it a bit better:

Front side bus

http://en.wikipedia.org/wiki/Front_side_bus

btw. running DDR2-800 (PC2-6400) ram on a CPU with a FSB of 1066 is fine, and vice-versa...

to change the speed of the RAM, you'd have to do it manually and enter the speed (memory clock) of the RAM to 266 mHz in the BIOS...



Ben

"If it works don't fix it! If it doesn't use a sledgehammer..."

 

[SkipCox]

OK. The E6850 runs at 333Mhz FSB, or as Intel calls it; 1333Mhz FSB. That's 4x333 (quad pumped).

PC2-8500 memory (DDR2-1066) is made to run at 533Mhz FSB so it would be 1066Mhz memory (2x533)

So, the correct memory for your machine would be PC2-5300 (DDR2-667).

To match CPU and memory FSB, we want to run 'em both at 333Mhz by using PC2-5300 or underclocking the PC2-6400 or PC2-8500 from 400/533Mhz respectively to 333Mhz.

The other alternative is to overclock the CPU to 400Mhz and use PC2-6400 memory or underclock the PC2-8500 memory to match that 400Mz FSB.

Clocking the CPU to 533Mhz would be overclocking the crap out of it...likely wouldn't happen.

Clear as mud?


Skip

 

[JSD7878]

Ok two different answers it seems, anyone else care to way in?

 

[SkipCox]

Ben is certainly not incorrect in saying;

"btw. running DDR2-800 (PC2-6400) ram on a CPU with a FSB of 1066 is fine, and vice-versa..."

That's an asynchronous system and is fine for some things like laptops or making a machine run with an overclocked CPU and memory that won't handle the speed of that overclock.

Here's another Wikipedia page;

http://en.wikipedia.org/wiki/Memory_divider

Skip

 

[cdogg]

Alright I'll take a stab...

First you have to understand how DDR2 is different from its predecessor, DDR. As we all know, DDR stands for "Double Data Rate" and essentially transfers twice as much data than plain SDRAM per clock cycle. It accomplishes this by using both the rising and falling edge of each cycle. So even though PC100 SDRAM and DDR-200 used the same 100MHz memory bus, clearly the advantage in data transfer went to DDR.

Enter DDR2. The same concept applies in using the rising and falling edge to "double-pump" the bus speed. However, what is interesting here is that DDR2 is also using a wider bus internally to connect its memory cells to the I/O buffer. The method is referred to as the prefetch. DDR uses a 2-bit prefetch and DDR2 uses 4-bit. In addition, the I/O buffer is running at twice the speed to accomodate all the traffic on the wider bus. So as a result, DDR2 is able to transfer twice as much data per clock cycle as DDR and four times as much as regular SDRAM.

You can see the concept illustrated here:

http://www.xbitlabs.com/articles/memory/display/ddr2-ddr_2.html

________________________________________________________


So what does all this mean?

Well earlier Skip told you that "[blue]PC2-8500 memory (DDR2-1066) is made to run at 533Mhz FSB[/blue]". This is just not true because DDR2 is actually "quad-pumping" the bandwidth of the FSB. So DDR2-1066 actually runs at full speed when the FSB is set to 266MHz.

Now your Core 2 Duo e6850 is using a 333MHz FSB, which is quad-pumped to a theoretical speed of 1333MHz. The optimum configuration then would be to couple it with DDR3-1333 memory. Obviously that's an option you know your motherboard doesn't support. So no matter what you do, your system is going to be asynchronous unless you upgrade to a DDR3 motherboard (not a smart option).

With that in mind, the best you can do with what you have is to bump up the DRAM speed setting to DDR2-1066 in your CMOS. The setting is found on this screen:

http://www.hardwaresecrets.com/fullimage.php?image=7740

________________________________________________________


Regarding asynchronous systems, they're not as bad as they used to be in the early days of DDR. In most real-world benchmarks involving DDR2 and DDR3 systems, we see that there isn't a whole lot of benefit in synching the memory to the CPU. Being off by a slight margin doesn't really hurt. That's why I wouldn't recommend going through the trouble of getting a newer motherboard.

FYI...
A copy of your manual might help sift through the CMOS settings if you need it:

http://www.uabit.com/downloads/downloads.php?file=/downloads/manual/english/ip35-pro.zip

~cdogg
"Insanity: doing the same thing over and over again and expecting different results." - Einstein
[tab][navy]For posting policies, click [/navy]here.

 

[BadBigBen]

cdogg - that was more than a stab, I think there is no easier way to put it and very clear to understand... HA*



can't add more to it, other than that I've been running my system with DDR2-800 ram and my CPU on a FSB of 1333 MHz...

Ben

"If it works don't fix it! If it doesn't use a sledgehammer..."

 

[JSD7878]

Just wanted to say thanks so much, I appreciate everyone's contributions.