# Word problems are problematic

You have just purchased some DDR3 memory that has a module name of PC3-12800. What memory clock rate would best match this DDR3 memory?

A) 100 MHz

B) 133 MHz

C) 166 MHz

D) 200 MHz

E) That’s a big number. I’m sure anything will work just fine.

#### The answer: D) 200 MHz

The calculation to determine the peak data rate is to multiply the memory clock rate by the bus clock multiplier (4), the data rate (2) and the number of bits transferred (64). That value is then divided by the bits per byte (8). To simplify this equation for DDR3, you can multiply the clock rate by 64 to determine the peak data rate. To reverse the equation, you can divide the peak data rate by 64 to determine the clock rate. In this example, 12800/64 is 200. ##### Want to know more? Watch “Identifying Memory Types.”

Memory comes in many shapes and sizes. In this video, you’ll learn about RAM, ROM, static RAM, dynamic RAM, synchronous DRAM, and how to calculate the throughput rates of DDR memory.