The Four Hundred

IBM's Microelectronics Division quietly announced, at COMMON two weeks ago, a new single-core variant of the Power4 processor that it hopes will begin shipping sometime in the second half of 2003. So what, you say? This could be an important development, and no one seemed to notice last week. This new Power4 chip, called the PowerPC 970, is a hot little chip, and it could just turn out to be the salvation of the iSeries line.

Before getting into how the 64-bit PowerPC 970--which surely should have been called Power4 Lite or something other than PowerPC, since PowerPC implies a 32-bit architecture, rather than 64-bit Power architecture--might save the iSeries line, let's compare and contrast the Power4 and its new sibling, the PowerPC 970.

The Power4 processor that is shipping today in the iSeries Model 890 and pSeries 630/670/690 servers is a dual-core chip. That means it has two whole Power processors on a single chip. Each core is a unified core that supports the instruction sets of the Star line of 64-bit PowerPC chips used in IBM's OS/400 and AIX commercial servers and the 64-bit instructions used in the Power3 line of chips, which have instructions aimed at technical computing but which have also seen some play in a few commercial AIX servers. The two Power4 cores on each chip share a united L1/L2 cache (which is 1.5 MB in size) that is also on chip. Each Power4 chip also includes interconnection electronics that allow up to four Power4 chips (that's eight cores) to be linked together in a single multichip module without any external wiring. The Power4s currently run at 1.1 GHz and 1.3 GHz. Follow-on Power4+ processors using an improved copper chip-making process are due in early November running at 1.2 GHz and 1.45 GHz, and before too long IBM is expected to crank up the clock to 1.6 GHz and 1.8 GHz on the Power4+ chips. With 170 million transistors on a single piece of silicon, the Power4 and Power4+ chips are big, hot, and powerful. They are also wickedly expensive to make, and they most certainly are not high-volume chips. They are, in fact, practically hand made.

Enter the PowerPC 970. The PowerPC 970 has the community of Apple PC users agog because, if Apple uses this chip, as it is widely expected to, the company will finally have a chip that can compete against what the Wintel and Lintel crowd is offering on desktops and in entry servers. According to my sources at IBM Microelectronics Division, the PowerPC 670--and this is the key thing, as far as iSeries and pSeries customers are concerned--supports the full Power4 instruction set, which is a superset of the PowerPC instruction set that Apple's MacOS and IBM's AIX 4.3.3 run on. This means the PowerPC 970 chip can run the 64-bit editions of OS/400, Linux, and AIX. IBM is testing the chip with Linux right now, in both 32-bit and 64-bit modes; Apple is testing out Mac OS X (which is really BSD Unix with a pretty face) on it as well.

The PowerPC 970 has a single Power4 core and will have 96 KB of L1 cache and at least 512 KB of integrated L2 cache. It will run 32-bit PowerPC code natively and will support 64-bit Power4 code natively as well. (The PowerPC chips were switchable between 64-bit and 32-bit modes as well, and at the instruction level, which is why the OS/400 PASE AIX runtime works on iSeries machines.) The chip is expected to debut at 1.4 GHz and 1.8 GHz, and it will eventually be clocked down to 1.2 GHz and clocked up to 2 GHz. The chip is being made at that new fangled 300mm wafer chip making facility in East Fishkill, New York, that IBM made so much noise about a year ago, and it will be the first chip that IBM makes using a 0.13 micron copper-SOI process married to the 300mm wafers. The PowerPC 970 supports SMP clustering (which is important for servers and workstations) and also includes a special vector processor, reportedly called VMX, that is compatible with the AltiVec vector processor that Motorola put into its PowerPC chips and that are used by Apple in its Macs, which currently top out at 1.25 GHz (way long in the tooth by Intel desktop processor standards). The chip supports a 900 MHz memory bus that supplies a peak 7.2 GB/sec of memory bandwidth. It has 52 million transistors and only dissipates 19 watts at 1.2 GHz and 42 watts at 1.8 GHz. This chip will be sampling in the second quarter of 2003, and it will be in production in the second half of next year.

If Apple uses this chip--and there is every reason to believe that it will--it will be a lot less costly to make than a real Power4 chip, and probably a lot less expensive than even a PowerPC S-Star chip. The PowerPC 970 could be the foundation of a great line of compact, inexpensive, yet powerful iSeries machines that can churn the installed base of AS/400 servers, unlike a Model 270--even with the Green Streak discount--can do today. I'll explore the possibilities in detail in next week's issue of The Four Hundred.