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Breaking the Hype of High Frequency RAM

Written on April 2, 2012 by Matt Bach
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Introduction

When it comes to computer hardware, it is very common for manufactures to offer a series of "Extreme" products in addition to their standard line of products. With video cards, this is often in the form of pre-overclocked cards. With motherboards, additional overclocking features are typically the requirement for an extreme motherboard. With memory, this is generally in the form of RAM that runs at very high frequencies.

We've talked about high frequency (or overclocked) RAM in the past with the blog post Overclocked Memory is a Scam, although much of that post is in regards to the various compatibility problems we saw when DDR3 was still young. Most of the compatibility problems have thankfully been resolved (although the faster RAM still tends to have a higher failure rate), but there are still a few problems with high frequency RAM.

The main issue with high frequency RAM is due to the fact that at higher frequencies (generally around 1866MHz and higher), memory manufactures also begin to increase the timings in order to keep the RAM stable. In this article, we will be looking to see if RAM with a higher frequency and increased timings has any performance advantages over RAM with lower frequency and reduced timings in a high-end computer systems using a dedicated video card. The effect of RAM is very different when using onboard CPU graphics, but we will leave that aspect of RAM performance for a future article.

To determine how this ratio of frequency to timings affects performance, we ran an extensive suite of benchmarks on multiple platforms with a range of RAM models. But first, let's go through the common RAM specifications to help us understand why timings are just as important as frequency.

RAM Specifications

There are three main specifications for RAM that determine its performance: size, frequency and timings. The size of RAM is easy enough to explain as it is simply the amount of data that can be stored within the RAM. Frequency is a bit tougher, but boils down to being how fast the computer can access the data that is stored on the RAM. Timing (also known as the CAS latency) is even more complicated, but is essentially how long the RAM has to wait between receiving a read command and when it is able to execute it. Another, slightly less accurate, way to think of it is how long the RAM to takes to find a requested block of data after receiving the read request.

Ideally, you want to have a large amount of RAM running at a high frequency with low timings. The problem is that in general, extreme RAM increases the frequency while also raising the timings. So while the computer can read data from the RAM faster, it takes it longer to move between different data sets which in most applications will negate the improvements brought about by the increased frequency. So to summarize:

Size: Amount of data the RAM can store
Frequency: Speed at which the computer can read the data from the RAM
Timings: How long the RAM has to wait between read commands

Test Hardware

In order to test whether a higher frequency at the cost of increased timings is worth it, we ran a series of benchmarks using the RAM listed below. For each frequency level, we used RAM with timings that are the most common at that frequency.


We have found in the past that the performance differences between brands (running at the same settings of course) are negligible, but we wanted to remove as many variables as possilble. We used Patriot RAM for our testing because they had three of the four most common RAM frequency/timing ratios. Patriot does not make a 1333MHz low latency kit with CL7 timings, however, so we tweaked the timings and frequency of the PC3-12800 model to run at those specifications. This will have the exact same performance as RAM that is designed to run at those settings, but may be slightly less stable. Luckily, our RAM performed just fine at those settings through all of our testing so stability was not an issue.

Due to the different ways that Intel and AMD processors handle RAM, we also performed all of our testing on platforms from both companies. Relevant specs are below:


In order to see if there are any performance benefits to using the high frequency, increased timing RAM, we divided our testing into three categories: Synthetic, Gaming and Application. The synthetic section covers simply the raw read/write speeds and latency of the RAM for each configuration. For the gaming and application sections, we ran a series of different benchmarks to measure any performance differences.

We ran a fairly extensive set of benchmarks, so we will only actively discuss the test results that we feel showed a notable difference in performance. The results from the other tests are still shown, but have been sized down to help keep this article from become too massive. Feel free to click on any picture to enlarge it to full size if you would like to take a closer look at those results, however.


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