the hardware, but may not represent the minimum amount of data traffic required to implement the user's code. For example, some computer systems have the ability to avoid write allocate traffic using special instructions, leading to the possibility of misleading comparisons of bandwidth based on different amounts of data traffic performed. Bandwidth computation and nomenclature The nomenclature differs across memory technologies, but for commodity DDR SDRAM, DDR2 SDRAM, and DDR3 SDRAM memory, the total bandwidth is the product of: Base DRAM clock frequency Number of data transfers per clock: Two, in the case of "double data rate" (DDR, DDR2, DDR3, DDR4) memory. Memory bus (interface) width: Each DDR, DDR2, or DDR3 memory interface is 64 bits wide. Those 64 bits are sometimes referred to as a "line." Number of interfaces: Modern personal computers typically use two memory interfaces (dual-channel mode) for an effective 128-bit bus width. For example, a computer with dual-channel memory and one DDR2-800 module per channel running at 400 MHz would have a theoretical maximum memory bandwidth of: 400,000,000 clocks per second × 2 lines per clock × 64 bits per line × 2 interfaces = 102,400,000,000 (102.4 billion) bits per second (in bytes, 12,800 MB/s or 12.8 GB/s) This theoretical maximum memory bandwidth is referred to as the "burst rate," which may not be sustainable. The naming convention for DDR, DDR2 and DDR3 modules specifies either a maximum speed (e.g., DDR2-800) or a maximum bandwidth (e.g., PC2-6400). The speed rating (800) is not the maximum clock speed, but twice that (because of the doubled data rate). The specified bandwidth (6400) is the maximum megabytes transferred per second using a 64-bit width. In a dual-channel mode configuration, this is effectively a 128-bit width. Thus, the memory configuration in the example can be simplified as: two DDR2-800 modules running in dual-channel mode. Two memory interfaces per module is a common configuration for PC system memory, but single-channel configurations are common in older, low-end, or low-power devices. Some personal computers and most modern graphics cards use more than two memory interfaces (e.g., four for Intel's LGA 2011 platform and the NVIDIA GeForce GTX 980). High-performance graphics cards running many interfaces in parallel can attain very high total memory bus width (e.g., 384 bits in the NVIDIA GeForce GTX TITAN and 512 bits in the AMD Radeon R9 290X using six and eight 64-bit interfaces respectively). ECC bits In systems