Q: What is DDR SDRAM?
A: DDR SDRAM stands for Double Data Rate-Synchronous DRAM, a type of SDRAM that supports data transfers on both edges of each clock cycle which effectively doubling the memory chip's data throughput.
Q: What is Dual Channel Memory?
A: Dual channel architecture simply takes the existing RAM technology to break the single channel bottleneck of memory bandwidth. With a second parallel channel added into chipset, the bandwidth of memory has greatly increased to boost up overall system performace.
In order to use Dual Channel Memory, your motherboard has to be capable of supporting this technique and you will also need two equal memory modules.
Q: What is CAS Latency?
A: Besides the speed of DDR1 and DDR2, there is additional information that tells you the memory performance. Those information are numbers like 2.5-6-3-3 1T, and the lower the better.1.2.5-6-3-3-1T
2.CL-tRas-tRCD-tRP-CMD
CL: CAS Latency. The time it takes between a command having been sent to the memory and when it begins to reply to it. It is the time it takes between the processor asking for some data from the memory and it returning it.
tRCD: RAS to CAS Delay. The time it takes between the activation of the line (RAS) and the column (CAS) where the data are stored in the matrix.
tRP: RAS Precharge. The time it takes between disabling the access to a line of data and begin of the access another line data.
tRAS: Active to Precharge Delay. How long the memory has to wait until the next access to the memory can be initiated.
CMD: Command Rate. The time it takes between the memory chip having been activated and when the first command may be sent to the memory. Sometimes this value is not informed. It usually is T1 (1 clock cycle) or T2 (2 clock cycles).
Q: I have 4GB of RAM but I am seeing only 3GB in Windows, why? What can I do to fix this?
A: Users reporting only 2.75GB~3.5GB being seen in Windows is an isolated, well-documented problem within 32-bit operating systems. This is due to Windows reserving and allocating a portion of your installed physical memory for hardware mapping and that portion of the memory will always remain inaccessible. Fully detailed reference can be found here http://support.microsoft.com/kb/929605/en-us.
There is no guaranteed fix for this problem and chances are you will never see anything close to 4GB. However, there are a couple of methods that MIGHT configure Windows to address full 4096MB of your physical memory but the portion that's being reserved for hardware mapping will remain that way. Note that you must first enable the "Memory Remap" feature in your BIOS. If it's not available it means your motherboard's chipset does not support 4GB RAM addressing even if the motherboard can detect up to 8GB or more.
*Disclaimer*: This information is being provided on our website for educational and referencing purposes only. The end result will depend on your chipset/BIOS and how well you have followed through the steps. In no way, under any circumstances, will GeIL and its staffs/affiliates be held responsible for what you do with this information. You are strongly advised to perform more research on this topic before utilizing the information provided herein. Currently, this is only available to Vista users.
Method 1. - Enable PAE Mode ( Physical Address Extension)
This method modifies Vista's system core to use 3 memory addressing cycles instead of 2 by default and it's theoretically slower, so you should disable this if you ever go back to a lower amount of RAM.
*a. Start>All Programs>Accessories>cmd, right-click on it and choose "Run as Administrator" to open up an elevated Command Prompt.
*b. Type this command: BCDedit /set PAE forceenable
*c. Hit enter, and you should see this message: "The operation has completed successfully". If you see this, exit CMD and reboot your computer.
If you don't see any change in RAM amount under Windows, you can try the second method below.
Method 2. -Disable DEP Mode. (Data Execution Prevention)
DEP allows Windows Vista to reserve a portion of your physical memory to monitor memory and kernel level data executions. If Windows thinks a certain program you're running is malicious, it will utilize DEP and prevent the program from being executed at all. This is a security feature to help protect your computer from mal-ware attacks and it is strongly recommended to be left untouched. But if you must free up as much memory as possible, then you may try this method but do this at your own risk.
*a. Start>All Programs>Accessories>cmd, right-click on it and choose "Run as Administrator" to open up an elevated Command Prompt.
*b. Type this command: BCDedit /set nx AlwaysOff
*c. Hit enter, exit out of CMD then reboot computer.
To turn DEP back on type the following command in CMD:
BCDedit /set nx AlwaysOn
