SLC is twice as fast as MLC, with maximum read speeds of about 14MB/sec. for writes, coming closer to - but not quite - saturating the USB 2.0 interface. USB drives combining four-channel controllers with MLC memory will reach speeds of about 60MB/sec. That will increase speeds even for slower MLC memory by increasing the number of lanes through which data can be written to and from the memory cells. In the first half of 2009, controller manufacturers will begin shipping drives with dual- and even four-channel controllers, says Pat Wilkison, vice president of marketing and business development at Stec, a manufacturer of memory and storage products. SLC stores one bit in each memory cell, and MLC stores two bits in each cell. The single biggest factor in USB drive performance is whether it contains one of two types of memory: SLC (single-level cell) or MLC (multilevel cell).
