As chief virtualization technologist, "my main focus now is looking at the bigger picture of IT complexity and cost, and how we can leverage virtualization as well as other technologies to get cost and complexity under control," he says. "We just can't afford to keep doing IT the way we do it today."

Rymarczyk watched with interest as adapted the concepts behind IBM's virtualization technology to x86 systems. In some ways, VMware's task was more difficult than IBM's because the and AMD x86 processors used in most corporate data centers were not built with virtualization in mind. With the mainframe, IBM has total control over both the hardware and virtualization software, but VMware had to overcome the idiosyncrasies of x86 hardware developed by other vendors.

Like IBM, "VMware is creating a virtual machine for every user. But they started before there was any hardware assist. It turns out the x86 architecture has some nasty characteristics," Rymarczyk says. To run Windows in a VM on an x86 platform, VMware had to intercept "difficult" instructions and replace them, he says.

"The x86 architecture had some things that computer scientists would really frown upon," he says. "Intel now has put in some hardware features to make it easier. They have started going down a similar path to what we did in the 1960s."While there was a clear need for virtualization on the mainframe in the 1960s, the idea of building hypervisors for new platforms was "effectively abandoned during the 1980s and 1990s when client-server applications and inexpensive x86 servers and desktops led to distributed computing," according to a of virtualization written by VMware.

In the 1980s and early 1990s, x86 servers lacked the horsepower to run multiple operating systems, and they were so inexpensive that enterprises would deploy dedicated hardware for each application without a second thought, Rymarczyk says. But chip performance has increased so dramatically that the typical Windows machine needs less than 10% of the processing power actually delivered by a server today, he says.