Intel ships the first Pentium processors, debuting with speeds of 60 and 66 MHz. With 3.1 million transistors and 4 GB of addressable memory, it was a significant upgrade from the 80486 line of processors. Also significant was the fact that Intel chose to brand this fifth generation of processors with a name that could be trademarked, departing from the 286, 386, and 486 sequence it had been using for their 8086 line of processors. The main reason for this was that AMD, who had been a second source manufacturer of x86 processors, reverse engineered Intel’s 386 processor after Intel tried to end their second source arrangement. AMD claimed that they had the legal right to manufacture x86 processors due to the contract it had with Intel. This started a long running legal feud between the two companies that lasted until 1995. Among various lawsuits, AMD successfully defended a trademark infringement claim brought about by Intel over the 386 name. The court ruled in March of 1991 that the term 386 was generic and could not be trademarked. Therefore Intel went to a marketing firm to come up with the name Pentium so it could differentiate itself from AMD’s eventual 586 clone.