Up to the early 1990s it was common to find EMS systems being delivered based on proprietary
hardware and
operating systems. Back then EMS suppliers such as
Harris Controls (now
GE),
Hitachi,
Cebyc,
Control Data Corporation,
Siemens and
Toshiba manufactured their own proprietary hardware. EMS suppliers that did not manufacture their own hardware often relied on products developed by
Digital Equipment,
Gould Electronics and
MODCOMP. The VAX 11/780 from Digital Equipment was a popular choice amongst some EMS suppliers. EMS systems now rely on a model based approach. Traditional planning models and EMS models were always independently maintained and seldom in synchronism with each other. Using EMS software allows planners and operators to share a common model reducing the mismatch between the two and cutting model maintenance by half. Having a common user interface also allows for easier transition of information from planning to operations. As proprietary systems became uneconomical, EMS suppliers began to deliver solutions based on industry standard hardware platforms such as those from
Digital Equipment (later
Compaq, then
HP),
IBM and
Sun. The common operating system then was either DEC
OpenVMS or
Unix. By 2004, various EMS suppliers including
Alstom,
ABB and
OSI had begun to offer Windows based solutions. By 2006 customers had a choice of
UNIX,
Linux or
Windows-based systems. Some suppliers including ETAP, NARI, PSI-CNI and Siemens continue to offer UNIX-based solutions. It is now common for suppliers to integrate UNIX-based solutions on either the Sun
Solaris or IBM platform. Newer EMS systems based on
blade servers occupy a fraction of the space previously required. For instance, a blade rack of 20 servers occupy much the same space as that previously occupied by a single
MicroVAX server. ==See also==