A few years ago, you wouldn't have bet much on IBM's Power systems having a bright future. The major Unix platforms have all been on the decline for more than a decade, giving way to Linux servers powered by increasingly capable x86 processors from Intel.
The jury is still out on Power, but there are signs that a bold push by IBM to revive the technology has started to pay off. Oracle's Sparc platform is also proving surprisingly resilient, raising a question about whether Hewlett-Packard should have killed its own proprietary Unix chip, PA-RISC, all those years ago.
IBM reported its financial results for the fourth quarter this week, and while overall sales continued their downward trajectory, the company reported the first growth for Power systems in four years.
The numbers aren't spectacular, but they're on the upswing. Last quarter, Power systems revenue climbed 4 percent from a year earlier, or 8 percent adjusted for the strong US dollar. On that basis, sales were up for all of 2015, too.
IBM doesn't release actual dollar figures for Power, only percentages. But it's clearly a turnaround from two years ago, when the business was tumbling more than 30 percent each quarter.
A big part of the reason is Linux. Two years ago, IBM said it would invest a billion dollars to make it easier for clients to run Linux as an alternative to AIX, its proprietary Unix software. Its newest Power8 processor includes changes that make it easier for clients to port Linux applications from x86.
IBM also opened up the platform to third parties, a big change to its business model. Under the OpenPower initiative, other companies can now design and sell Power servers and processors under license from IBM. And IBM is adding more components to its systems from third parties like Nvidia and Mellanox.
Those moves have helped it to reposition Power for modern workloads like big data and cloud applications. It released a new line of low-cost Linux servers that customers can order online. Even Google was testing Power servers for its data centers, though it's unknown if it plans to use them.
Nathan Brookwood, principal analyst at Insight64, said customers want choice. "Everybody is looking for an alternative to Intel," he said.
ARM servers are taking longer than expected to gain traction, and right now Power seems like the only viable alternative, he said.
Brookwood questioned whether IBM can sustain the growth long term. Vendors including Qualcomm are investing heavily in ARM server chips, and Power could eventually find itself "squeezed out" by Intel and ARM, he said.
IBM also hasn't discussed plans yet for future Power processors. "That's key, because Intel invests seriously in this area, and the ARM partners in aggregate are investing a lot."
Still, for now IBM's RISC chip is having a mini-renaissance.
Meanwhile, Oracle continues to pile money into Sparc, confounding predictions that Chairman Larry Ellison would kill off the architecture after buying Sun Microsystems. Oracle tends to focus on systems that run its own applications, however, while IBM is going after a broader market.
The RISC platforms give both companies a way to differentiate their products from commodity hardware based on x86 processors.
HP doesn't have that option. It killed off PA-RISC a decade ago and bet big on Intel's Itanium chip with disastrous results. Itanium eventually flopped, and HP is having to port its high-end systems to Intel's Xeon.
"I think they gave up on PA-RISC for all the wrong reasons," Brookwood said. HP was worried about the cost of building new chip manufacturing plants, he said, and didn't foresee the rise of third-party foundries like TSMC.
The efforts with Power are part of a broader effort by IBM to make its hardware profitable again. It sold its money-losing x86 server business to Lenovo to focus on higher end products. Its System z mainframe had a good 2015 as well, thanks to the release of the z13 early last year.
The upshot is a much smaller but more profitable hardware business. For all of 2013, IBM's hardware division reported a loss of $507 million on $15 billion in revenue. Last year, it made a profit of $604 million on $8.0 billion in revenue.