IBM is merging two of its server lines -- System i and System p -- into a single family of products, a move that was widely applauded but led some to ask: What took you so long?

When the two server lines were born almost two decades ago they were based on very different hardware and software. They still use different software -- System p comes with Linux or IBM's AIX flavor of Unix, while System i comes with IBM's integrated i5/OS stack. But the hardware platforms have merged to become almost indistinguishable, with both families using IBM Power processors and similar components and peripherals.

One result of that evolution is that System p customers enjoy lower hardware prices, driven down by competition in the Unix server market, while System i customers pay more for what have become essentially the same components, said Dan Olds, principal analyst at Gabriel Consulting Group, in Beaverton, Oregon.

Combining the two product lines erases that artificial price distinction, he said. "It also reduces complexity a whole hell of a lot. That's the real story here."

The two server lines have been merged to create the Power Systems family, based on IBM Power6 processors. Each new system will be offered with AIX, Linux or the i5/OS, which has been renamed simply "i" as part of the announcement, said Scott Handy, vice president of worldwide marketing and strategy for IBM's Power Systems group.

IBM was due to make the announcement Wednesday at the Common user group conference for System i users in Nashville, Tennessee. It also announced three servers from the new family, aimed at smaller businesses, and said it would detail its high-end server plans next week.

"This is a really big day for us and for a lot of customers, and it's been a long time coming," Handy said. "We started this about 10 years ago, putting a plan together to fully integrate these two product lines."

The System i family began life in the late 1980s as the AS/400, based on a custom IBM processor. The i5/OS is an integrated software stack including IBM's DB2 database, an application server and security software. The System p was born in about 1990 as the RS/6000 and used IBM's Power processors and AIX operating system. It is now also offered with 64-bit Linux.

Despite using similar components, part numbers for the two server lines have been different. "So the same four-digit feature code for one family might have been a power cable, and for the other it was a memory card. So for customers who were dealing with both environments it was a little complicated," Handy said.

Joe Clabby, president of Clabby Analytics in Yarmouth, Maine, said he toured an AS/400 plant in 1999 and wondered then when IBM would merge the two product families.

"They were using the same parts as they used for the RS/6000, and it just jumped out at you -- why create completely separate CPUs and separate frames and chassis when they should be combining those systems? And this was almost 10 years ago."

Olds put the delay down to "inertia" and the internal politics of merging two big product groups. "Who wants to merge their organization? When you do that there's less chairs left."