The new chip set expands memory and I/O bandwidth and capacity for HP's low-end Itanium servers. HP said the 266-MHz data rates for PCI-X are adequate to serve the various multiport Fibre Channel and Gigabit Ethernet cards it plans to offer. The delay in Express support is due to the need to respin the I/O chips in the new ZX-2 offering.

All of HP's existing servers can accept the dual-core Itanium as an upgrade. But the company specifically respun its ZX-1 ASIC for low-end systems to add Express and a handful of other enhancements.

The company announced two new servers using the ZX-2 chip set. The RX3600 is a 4U-size server with two Itanium CPUs, eight Serial-Attached SCSI drives and eight PCI slots, two of them capable of 266-MHz data rates. The RX6600 is a 7U server with four CPUs, 16 SAS drives and eight PCI slots.

HP is by far the leading vendor for Itanium systems, a processor architecture it codeveloped with Intel Corp. Focused on big data center servers, Itanium has narrowed its role from its original ambitions of replacing the x86.

The Montecito version of Itanium is a 90-nm CPU running at up to 100 W with two cores each supporting two threads. It has a 533-MHz front-side bus, but the new HP chip set is rated to support the 667-MHz front-side bus of the follow on to Montecito.

The ZX-2 chip set comes in three parts: A memory controller with I/O cache links to the CPU bus; multiple I/O adapter chips are used to fan out I/O slots: and memory expander chips can be added as needed for capacity or bandwidth.

The chip set now supports 10Gbytes/s maximum I/O throughput, up from 4 Gbytes/s in the ZX-1. Latency for DMA reads has declined from 700 to 400 nanoseconds.

The chip set supports up to 385 Gbytes of DDRII memory running at 533 MHz, up from a total of 256 Gbytes of DDR at 266 MHz with the ZX-1. Memory bandwidth has jumped from 8.5 to 17 Gbytes/s and latency has decreased from 90 to 60ns.