Memory Timing

Don’t get glassy-eyed at the sight of those obscure names for RAM timing. XOTIC PC is in the business of building high-end computers from the ground up, and we know just how difficult it can be to dive headfirst into the world of PC terminology. In this guide, we’ll review the basics of memory timing, so you can understand the differences in transfer rates and maximum clock speed, as well as memory chip and module classification. With this information, you will also gain a basic understanding of overclocking, performance, and other essentials. Keep reading to learn more!

Shortcut to Memory Timing
Why is it important to understand how RAM speed and timing work? Premium memory enables your computer to run at high clock speeds and lower latencies. In layman’s terms, your PC will be optimized to process a very high volume of data messages with minimal delay. Every memory package features a series of numbers that symbolize timings in the following order: CL-tRCD-tRP-tRAS-CMD. Join us as we take a closer look at what each of these timings means.

CL (CAS Latency)
Example timing: 9-10-11-24-2
Access time allows you to determine the time it takes between a command that was sent to the memory and when it begins to reply to it. Determining is actually quite simple, if you divide the column access time by the clock cycle time. Just raise the result to the next whole number.

tRCD (RAS to CAS Delay)
Example timing: 9-10-11-24-2
Your computer’s data storage location is arranged in a matrix. The RAS to CAS delay determines the time between memory accessing RAS (Row Address Strobe) and CAS (Column Address Strobe). The lower the number, the better, but tRCD timing plays a less significant role in overall performance compared to CAS latency.

tRP (RAS Pre-charge)
Example timing: 9-10-11-24-2
Once data retrieval from the memory is successful, the row that was used to access that data needs to be closed, so that a new row can be accessed. RAS pre-charge determines the time it takes between disabling access to a line of data and the beginning of access to another line of data. If you already have a row selected, you will have to wait this number of cycles before selecting a different row.

tRAS (Active to Precharge Delay)
Example timing: 9-10-11-24-2
Otherwise known as Row Active Time, this figure regulates how long the memory has to wait until the next access to the memory can be acted upon. This timing usually needs to be greater than or equal to the sum of the previous three latencies, and it has one of the most significant effects on performance.

CR or CMD (Command Rate)
Example timing: 9-10-11-24-2
Command rate stands for the time it takes from memory activation to the possibility of an action being delivered to it. As a general rule of thumb, CR1 provides better performance and CR2 provides more stable overclocks.

Before rushing off to upgrade RAM, you should always check the motherboard manufacturer’s memory support list. Older motherboards may be more difficult to find compatible memory components. If you have any questions about memory timing or would like to learn more about building your own custom PC, please contact us today to speak with an experienced representative for additional information or further assistance.