SEATTLE Two new implementations of the emerging serial PCI Express interconnect are in the works, according to presentation at the Windows Hardware Engineering Conference here Thursday (May 6). Engineers are developing a cabled version of Express as well as a plug-and-play server module.
Express is a 2.5 Gbit/s serial interconnect designed by Intel Corp. and a group of its partners as the successor to the parallel PCI bus. It is expected to appear initially in a variety of desktop, notebook and server systems this year.
The PCI Express Cabling work group kicked off last August and has completed a 0.3 draft spec. It expects to finish its spec in the first quarter of 2005.
The spec will define a seven meter cable and connector scheme for carrying x1 to x16 links of the Express interconnect. The cable will support a small set of additional signals for a reference clock, presence detection and power.
The cable is aimed at supporting a variety of uses. Desktop PC makers foresee Express cables linking separate display/drive units with under-the-desk compute/graphics boxes. Server makers want to link computers to expansion I/O systems. Test gear makers see the cables replacing existing MXI or PCI cables that link their gear to PCs.
The first generation of the cable spec will probably not be able to support the anticipated next-generation signaling spec for Express because the so-called Gen2 spec is still in an early stage of definition.
Wil de Bont, a principal hardware engineer with National Instruments is co-chairing the work group that includes a mix of 16 OEMs, chip makers and cable/connector companies.
A separate work group is developing a new PCI Express module for server I/O adapters. The modules are intended to be a more powerful and easy-to-use version of today's server I/O cards with better EMI handling.
The modules will come in two sizes. The single-wide module is roughly the same size as today's half-size PCI cards, handles 25 W power, 27 inches2 of pc board space and up to a x8 link of Express. A double-wide version handles 50 W power, 54 inches of pc board space and two x8 Express links.
The modules have a predefined airflow to ease server thermal design. They can also accommodate up to four Serial Attached SCSI or Serial ATA storage interfaces, said Eddie Reid, an Intel engineer leading the work group.
The module is currently in a version 0.6 draft with work expected to wrap up in the late fall. Adaptec, AMD, Dell, Emulex, Hewlett-Packard, IBM, Intel, LSI Logic and Microsoft are among the companies working on the spec.