What Is RAM Timing?

This updated guide examines What Is RAM Timing? and organizes the essential facts, background, and practical takeaways in clear American English.

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Find the clock speed of RAM

You can find the speed of RAM on the box or module by software like CPU-Z or in the BIOS / UEFI. The full name of the RAM module should look like this:

DDR4 3200 (PC4 25600)

DDR4 describes the generation of DDR that the chip is compatible with. The same number (2, 3 or 4) that appears on a PC indicates the same thing.

The first 4-digit number, 3200 in this example, is usually the RAM clock speed in megahertz. This figure actually refers to the data rate, measured in megatransfer per second or 10⁶data transmission operations per second.

In DDR RAM, the actual clock rate is half the data read speed, 1600 MHz in this example. Although that speed has been increased from the 400 MHz internal clock speed of RAM through the pre-fetch bits it is multiplied many times. But because DDR data transfers double the clock speed, the effective clock rate is twice the actual clock rate. Therefore, the effective data rate is equivalent to the apparent clock speed of RAM in MHz.

The PC number, 25600 in this example denotes the transfer speed measured in megabytes per second (MB / s). By multiplying the data rate (in megatransfer) by the width of the I / O bus (64 bits in all modern motherboards), we can determine the maximum possible transfer rate:

3200 megatransfer per second x 64 bits on transfer / 8 bits per byte = 25600 MB / s

Each figure indicates the same information, RAM speed but different form.

What is RAM timing?

Timing is another way to measure RAM speed. Timing measures the delay between various common operations on RAM chips. Latency is the time delay between activities. It can be considered as timeout.

We measure RAM timing in the clock cycle. Retailers list timing with four numbers separated by dashes like 16-18-18-38. The smaller the number, the faster the speed. The order of the numbers tells you what they mean.

First Number: CAS Latency (CL) Parameters

This is the memory time it takes to react to the CPU. But CL is not considered separately. This formula converts CL timing into nanoseconds, based on the transfer rate of the RAM.

(CL/Transfer Rate) x 2000

As a result, slower RAM has lower actual latency if there is a shorter CL.

The second number: TRCD

RAM modules use grid-based design to write addresses. The intersection of horizontal rows and columns denotes a specific memory address. The T_RCDparameter measures the minimum delay between entering a new row in memory and starting to access the columns in it. You can think of it as the time it takes for RAM to reach the address. The time it takes to receive the first bit from a previously inactive row is T_RCD+ CL.

Number three: TRP

Row Precharge Time (T_RP) measures the latency associated with opening a new row in memory. Technically, it measures the delay between issuing a precharge order to wait (or close) one row and the activation order to open another row, similar to the second number. The same factors affect the latency of both operations.

Number four: TRAS

Row Active Time (T_RAS) measures the minimum number of cycles a row needs to remain open to record appropriate data. Technically, it measures the delay between orders triggered on a row and precharge orders on the same row or the minimum time between opening and closing. For SDRAM module, perform T_RCD+ CL to calculate T_RAS.

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These delays limit RAM speed. The RAM controller handles these timing, meaning they can be adjusted (if the motherboard allows it). You can increase RAM performance by overclocking and setting timing in a few cycles.

RAM overclocking is the most common hardware overclocking technique, which requires the most testing. But faster RAM shortens the processing time of RAM usage, improving the rendering speed and responsiveness of the virtual machine.