Five years after AMD, Intel has produced its first CPU with an integrated memory controller. The AMD design was ahead of the game in a number of areas, and market leader Intel has integrated ideas from its competitor into the new Nehalem architecture. Until now, Intel has manufactured its quad-core processors from two dual-core dies. AMD always maintained that there was only one company that could build real quad cores — a distinction that Intel pooh-poohed. Now even that distinction has been lost: Nehalem (Core i7) CPUs consist of a single chip.
But that's not the end of the story. AMD processors communicate between themselves and with peripherals using AMD's Hypertransport, a point-to-point switched interconnect that maintains high bandwidth through ad-hoc independent channels. That technology contrasts with Intel's approach of having chips use the frontside bus to address not only memory but also to connect to other system components, sharing that channel between devices. That's no real disadvantage with single-core systems, and Intel has maintained performance in dual-core and quad-core systems by using large amounts of cache.
However, this old-fashioned way of communicating is a bottleneck for servers with multiple sockets. In the long term, even the 64MB on-chip cache with snoop filtering that Intel offers in its Xeon 7300 chipset or the 16MB Level 3 cache recently introduced into the six-core Dunnington could not help the chip giant remain competitive with AMD in the server field.
Intel's answer is to provide the Nehalem architecture with a technology called Quick Path Interconnect (QPI) that is comparable with Hypertransport. QPI is in the Nehalem desktop variants, codenamed Bloomfield, that are available later this month. The server variant, Gainestown, for two-socket systems is to follow in the first quarter of 2009, according to Intel boss Paul Otellini. Intel plans on introducing Nehalem chips for multi-processor systems in the second half of 2009, and QPI will also be part of Tukwila, the next generation Itanium processor, due at the end of this year.