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What is the deal with memory ?
To understand this we'll start off with the ordinary A-B-C of RAM memory. Random Access Memory, or volatile memory, is used by the system to store data for processing by a computer's central processing unit (CPU), also known as the processor. RAM stores the data in memory cells that are arranged in grids much like the cells are arranged in a spreadsheet, from which data, in the binary form of 1's and 0's, can be accessed and transferred at random to the processor for processing by the system's software. The faster that process goes up-to a certain threshold, the better your performance can be. When the computer is turned off, all of the data in the RAM memory is lost, hence its alternative name of volatile memoryUp to a point, adding RAM (random access memory) will normally cause your computer to feel faster on certain types of operations. Some applications (think Photoshop or most movie editing and animation packages) need bags of RAM to do their job. If you run them on a PC with too little RAM, they swap constantly and run very slowly. You can get a massive speed boost by adding enough RAM to eradicate the swapping. Programs like these seriously can run 10 to 50 times faster once they have enough RAM. This is no joke.
How does RAM work ? Well, the essence is actually very simple. To store a 1 in the memory cell, a capacitor is filled with electrons. To store a 0, it is emptied .. that's it .. it's that simple. The dilemma with the capacitor's container is that it has a leak. In a matter of a few milliseconds a full bucket becomes empty. Therefore, for memory to work, either the CPU or the memory controller has to come along and recharge all of the capacitors holding a 1 before they discharge. To do this, the memory controller will read the memory and then writes it right back. This refresh operation happens automatically thousands of times per second.
Always make sure you buy two bars so that you can have a dual-channel memory configuration, dual channel effectively double's the memory bandwidth and processors loves that bandwidth for sure as it can have a nice impact on overall performance.
So keep this in mind, performance and stability of any system depends in part on the memory being used and the settings for the RAM timings. Many users may have their preference for low-quality class-B brands; but certainly using brand name memory is a very good idea since low quality memory is often at the root of many stability issues.
However, always pay attention to the timings of the memory being used.
Oh wise Guru .. what are memory timings ?Let's explain a little what you will run into with memory timings. First off latency. We used the word numerous times already in this article. Latency is the time between when a request is made and the request is answered. I.E, if you are in a restaurant for a meal, the latency would be the time between when you ordered your meal to the time you received it. Therefore, in memory terms, it is the total time required before data can be written to or read from the memory. Thus lower is better.
Then we notice on the packaging is this: 5-5-5-18 (2T) for the OCZ2RPR11502GK 2 GB kit. What do the numbers mean ?
5-5-5-18 (2T) refers to CAS-tRCD-tRP-tRAS CMD (respectively) and these values are measured in clock cycles.
CAS Latency
Undoubtedly, one of the most essential timings is that of the CAS Latency and is also the one most people can actually understand. Since data is often accessed sequentially (same row), the CPU only needs to select the next column in the row to get the next piece of data. In other words, CAS Latency is the delay between the CAS signal and the availability of valid data on the data pins (DQ). Therefore, the latency between column accesses (CAS), plays an important role in the performance of the memory. The lower the latency, the better the performance. However, the memory modules must be capable of supporting low latency settings.tRCD
There is a delay from when a row is activated to when the cell (or column) is activated via the CAS signal and data can be written to or read from a memory cell. This delay is called tRCD. When memory is accessed sequentially, the row is already active and tRCD will not have much impact. However, if memory is not accessed in a linear fashion, the current active row must be deactivated and then a new row selected/activated. It is this example where low tRCD's can improve performance. However, like any other memory timing, putting this too low for the module can result in instability.tRP
tRP is the time required to terminate one one Row access and begin the next row access. Another way to look at this it that tRP is the delay required between deactivating the current row and selecting the next row. Therefore, in conjunction with tRCD, the time required (or clock cycles required) to switch banks (or rows) and select the next cell for either reading, writing or refreshing is a combination of tRP and tRCD.tRAS
Memory architecture is like a spreadsheet with row upon row and column upon column with each row being 1 bank. In order for the CPU to access memory, it must first determine which Row or Bank in the memory that is to be accessed and activate that row via the RAS signal. Once activated, the row can be accessed over and over until the data is exhausted. This is why tRAS has little effect on overall system performance but could impact system stability if set incorrectly.
Command Rate
The Command Rate is the time needed between the chip select signal and the when commands can be issued to the RAM module IC. Typically, these are either 1 clock or 2.
Memory testing is a process of trial and error, find and seek the maximum. This is pretty much a sucker for your free time.
If you are going to overclock then increase the FSB, change the memory timings, but most of all alter memory dividers until your system won't boot. If you are not comfortable with such a thing, hey this isn't your game then. I recommend you to lower the processor's multiplier and then slightly increase the FSB with high memory timings and take it from there timings wise.
Fact is that today's Intel processors really are dependant on memory bandwidth, the faster the better. Something is by far not as important for AMD processors.
Windows 98, who didn't use that OS? What amount of memory did your PC have? Right, likely 128 MB.
Over the years we progressed and noticed that applications have gotten more and more memory intensive. With Windows XP we moved towards 512 MB as standard to prevent the OS from swapping to the HD, and as explained on the previous page with the latest games we see that the certain games really like 1 GB. All this has happened over just a couple of years my friends.
Then Microsoft launched Windows Vista, the biggest memory hog in the world. 1 GB is just be the average recommended specification. They actually recommend 2 GB. See .. 2GB isn't that special anymore.
The OCZ memory we'll be testing today is two bars of 1 GB (in dual channel mode you gain the best memory bandwidth). The modules are tagged as
OCZ2RPR11502GK and have some pretty audacious 5-5-5-18 timings (for DDR2 memory). You'll notice the "9200" on the packaging sticker .. divide that number by eight and you'll notice that this memory is rated at 1150 MHz at these specific timings. For two GB of memory these are really nice timings.Let's have a peek at the modules.
