Question

A DDR4 DIMM running at a speed of 2666 MHz has what PC rating?

1) PC₄-17000
2) PC₄-24000
3) PC₄-21300
4) PC₄-30000

Answer 1

A DDR4 DIMM running at 2666 MHz has a PC rating of PC₄-21300. The PC rating is derived from the clock speed and the transfer rate formula, which considers the double data rate nature of DDR memory.

Step-by-step explanation:

When you have a DDR4 DIMM running at a speed of 2666 MHz, the correct PC rating to describe its performance is PC₄-21300. To understand why, let's consider how these ratings are calculated. The DDR4 naming convention uses the theoretical maximum transfer rate of the memory module, which is derived from its clock speed. The formula to convert the clock speed to the transfer rate is as follows:

• The DDR memory transfers data on both the rising and falling edges of the clock signal (hence, "Double Data Rate").
• Therefore, you take the clock speed (in this case, 2666 MHz) and multiply it by 8 (since there are 8 bits in a byte).
• As a result, 2666 MHz × 8 equals 21328 MB/s.
• The PC rating is labeled in units of 1,000 MB/s, so we round 21328 MB/s to the nearest thousand, which is 21300.
• Therefore, a DDR4 DIMM with a clock speed of 2666 MHz is labeled as PC₄-21300, which is option 3.