WinSSD uses the 511-bit pseudo-random test pattern defined in the ITU document O.153 section 2.1. This pattern is one bit short of being 64-bytes long. The first bit of the second iteration of the pattern begins as the last missing bit of the previous pattern. The pattern “wraps” around shifted by one bit each time it is sent. A buffer of 511-bytes will hold exactly eight copies of the 511-bit pattern, which is what the Sealevel WinSSD utility is programmed to send and receive. A copy of this pattern is included in the text file below.