Problem with 4gb Corsair Dominator

[Giantsdpk]

I have a Dell Xps 700 pc. I recently upgraded it to a Xps 720. The mobo is a NVIDIA nForce® 680i SLITM Chipset for Intel (D)3. I have 4x 1g DDR2 Corsair Dominator 800mhz. I can only get 2g 2x dimm to boot in either slot 1,3 or slot 2,4. I cant get all 4gb to boot. I have Windows Vista 64bit installed. If anyone has any ideas I would appriciate it. If it is a overclocking issue. Does anyone know how to change the voltage of ram in a Dell Xps 720?

[DerekT]

With four banks you will very likely need to drop your DRAM throughput from 800Mhz to 667Mhz. The motherboard memory controller is having issues with 4 DRAM banks filled. This is very common as most motherboards are optimized for two banks filled.

 

The memory controller can not keep up with the extra DRAM at the rated 6400 speed. You will need to drop the speed of the DRAM from 800Mhz to 667Mhz. If you had purchased 4 X 1024MB of PC8500 (1066Mhz) DRAM, then you would have had to drop to PC6400 (800MHz) DRAM, etc. 2 X 2048 will not issue this problem. This is a problem of all 4 banks being populated.

 

Think of it this way. If you have a small phone book, then when you go into the index to find the page where you will find the phone number you are doing so at a certain speed due to the pages of the Index. Then you have to drive through the pages to get to the number. Now if your index is twice as large and the pages twice as many, then it takes longer to access the data. Now DRAM has a Strobe and the length of the strobe is how long the rows and columns can be left open before they must be refreshed. There is not enough time for the dram to be refreshed and then accessed with 4GB at the full access speed of the DRAM. The chipsets are optimized for 2GB, not 4GB and for 2 DRAM slots, not 4 DRAM slots populated. You can overclock the FSB (and hence the Memory Controller Hub = MCH) to gain some extra bandwidth and thus access the capabilities of the DRAM since the chipset is now clocked up. Usually when you clock up the FSB and concurrently the Memory Controller Hub (MCH) you need to raise the voltages of the CPU/MCH a bit as well.

 

Think of it like a car that is slated to run the 1/4 mile in 10s. If you add another few thousand pounds to the car, it will not make the 1/4 mile in 10s. The DRAM needs to be slowed down, to keep up with the onboard memory controller.

[Giantsdpk]

Is there some software that will help with bringing down the voltages? I also did something that might have been stupid I used Ntune to autotune my PC with on of the 2gb 2x 1 dimm in then I switched and did it for the 2nd pair 2gb 2x 1 dimm. Then put all 4 dimm 4g and was hopeing it would change the voltage on each to the same lvl. I am pretty new to overclocking. I dont think Dell Xps has overclocking settings in the bios. I think they say to use Ntune. Is there a way to manually change voltages?

Strange that I heard of someone overclocking there 800mhz to 1066mhz with the same machine.

[DerekT]

Is there some software that will help with bringing down the voltages? I also did something that might have been stupid I used Ntune to autotune my PC with on of the 2gb 2x 1 dimm in then I switched and did it for the 2nd pair 2gb 2x 1 dimm. Then put all 4 dimm 4g and was hopeing it would change the voltage on each to the same lvl. I am pretty new to overclocking. I dont think Dell Xps has overclocking settings in the bios. I think they say to use Ntune. Is there a way to manually change voltages?

Strange that I heard of someone overclocking there 800mhz to 1066mhz with the same machine.

 

Use Ntune and set all default again. Remove/uninstall Ntune. Enter your BIOS and load Default settings. Save Default settings. Go to your DRAM speed and set it to 667Mhz. Save settings (not default again) and reboot. You will then have your system set back to default and set your DRAM to 667Mhz.

 

Results?