Chips We Really Need

The Power4's design reflects not mere pursuit of benchmark numbers but throughput for next-generation tasks.

Youve seen the TV auto ads that warn, "Professional driver, closed course. Do not attempt." They remind me of microprocessor companies dueling over which has the fastest chip. The benchmarks they cite recall the empty city streets, deserted mountain roads and other venues beloved of ad directors but rarely encountered in day-to-day driving.

Perhaps "do not attempt" was the warning that should have been given to Hewlett-Packard recently before it tried to corner on two wheels by announcing its HP Workstation xw4100 with an Intel 3GHz Pentium 4 CPU and an 875P chip set. Later on the day of the announcement, Intel admitted that this combination had shown "anomalies" in behavior (that have since been resolved).

One had to wonder which users had been impatiently awaiting this desktop dragster; even on the most intensive applications, HP predicts less than a one-fourth reduction in task times, with only "up to 5 percent" improvement in mainstream applications. To put these figures in automotive terms, the 0-to-60 time could fall from 7 seconds to 5.5, but the 15-minute drive to the store would lose only 45 seconds.

In the world that we see over our steering wheels, that sounds like the kind of improvement that we could get by learning to avoid the slow lanes and to time the traffic lights. Its less than I would want from putting a turbocharger on my minivan and is less than you should get from putting new workstations on the desks of our engineers or portfolio analysts.

In contrast, one processor chip has achieved a noteworthy track record for real-world performance: Im talking about IBMs Power4 processor. Its design reflects not mere pursuit of benchmark numbers but throughput for next-generation tasks.

The two CPU cores on a single Power4 chip share more than 100GB per second of bandwidth to their shared L2 cache and more than 55GB per second to memory. Personally, I overflow on numbers that big; perhaps, like me, youll find it easier to think of 55GB as 26 hours of DVD video—a stupefying amount of data. And the IBM eServer p655 series, shipped late last year, can hold four- and eight-processor blocks that stack up to 128 Power4 processors per frame.