A four-way server is a server that incorporates a multi-core processor for increased performance. Ideally, a four-way server would be four times as powerful as a server using a single-core processor. In practice, performance gains are somewhat less than that.
Multi-core processing has become a growing industry trend as single-core processors reach their practical limits of performance. In the past several years, two-way servers and four-way servers have become especially popular among medium-sized and large businesses.