Ahead of Siggraph next week Intel decided to lift its skirt and pass around the paper it’ll read there describing Larrabee, its new hydra-headed x86 graphics accelerator architecture meant to take on Nvidia and AMD’s graphics arm ATI in late ’09-early 2010.

The operative word that is supposed to make Nvidia and ATI quake in their boots is x86.

Properly speaking Larrabee is both a GPU and a CPU, a GCPU – graphics-capable processing unit – a chip Intel calls “the industry’s first many-core Intel architecture – and everybody knows the 30-year-old x86 instruction set, which will make the dingus compatible with all the x86 software out there.

As far a new architectures go, Intel isn’t going to make the Itanium mistake twice.

Like Intel’s original intentions for Itanium, Larrabee is supposed to be ubiquitous and go into everything from game PCs (initially as add-in accelerators) to handhelds to supercomputers.

Intel isn’t saying how many cores a Larrabee chip will have; maybe somewhere between eight and 48 Pentium-derived doohickeys to start – depending on linear performance – building to hundreds (and then thousands) over time like Nvidia with its 240 and ATI with its 800.

Unlike Nvidia and ATI, Larrabee uses software to emulate hardware-derived functionality (it has its own on-board micro-operating system) – a point of attack for its competitors.

On the plus side, it has a large delay-impeding cache (256KB L2 cache per core) and a very fast intra-core communication system designed as a 1,024-bit-wide bidirectional ring bus equally split in each direction. It also supports parallelism, 64-bit operations, multi-threading and ray tracing-based photorealism as well as DirectX and OpenGL libraries.

Figure it’ll do upwards of 2GHz.

GPU camp follower Jon Peddie figures the market Intel is shooting for could be good for 46 million units in 2010, the first full year of Larrabee shipments, and, assuming Intel can sell the chips for $100, represents a market value of $4.6 billion.

A lot depends on knocking ATI and Nvidia arse over tea kettle.

Peddie, by the way, expects Larrabee development systems in November. Intel is anxious to build a ecosystem and infrastructure for the thing.