Sun eyes 256-threaded server

Sun Microsystems is working on a version of its T2 processor for use in two-way and four-way servers, the company is set to reveal today at the Hot Chips conference at Stanford University in California.

Codenamed Victoria Falls, the chip's die area and power use is "comparable" to the T2, or Niagara 2 processor, according to slides of the presentation by Stephen Phillips, a distinguished engineer at Sun.

The main difference, however, is that Victoria Falls allows for two-way and four-way servers, whereas Niagara 2 is limited to single-processor systems.

Given the eight cores with eight threads each for the current T2 processor, a four-way system will be capable of executing 256 calculations simultaneously.

Sun had previously leaked titbits of information about Victoria Falls, but Tuesday's presentation will provide the most details yet.

The expansion into two-way and four-way systems poses a challenge for the chip's memory management.

Data can now be stored in either external memory or on another chip's cache memory. But, as the chip is forced to fetch data from outside the processor, overall performance can slow down significantly.

Sun plans to address these memory challenges by adding multi-chip coherence links that will route the processor to its externally stored data.

The two-way Victoria Falls chips are equipped with two so-called 'embedded coherence hubs' allowing data transmission rates of 65Gbps.

The four-way model offers double the amount of embedded coherence hubs, allowing for twice the transmission rate. The four-way systems also gain four external coherence hubs.

A two-way system performing an online transaction processing application will perform at a rate of 180 per cent of a single processor system, Sun claimed.

A 'Java Business' benchmark came in at 185 per cent and 'CPU intensive' application logged 192 per cent. Sun did not provide performance projections for its four-way systems.

Sun unveiled Niagara 2 earlier this month. Systems powered by Victoria Falls chips are scheduled to ship in early 2008.