Information Technology Reference
In-Depth Information
2. The bus enumerator locates and gathers information from either the device drivers or the
BIOS services for that particular device type. For example, the CD-ROM bus enumerator
calls the CD-ROM drivers to gather information.
3. Each of the drivers is then loaded and they wait for the configuration manager to assign
their specific resources (such as IRQs, I/O addresses, and so on).
4.
The configuration manager calls on resource arbitrators to allocate resources for each de-
vice.
5. Resource arbitrators identify any devices which are conflicting and tries to resolve them.
6. The configuration manager informs all device drivers of their device configuration. This
process is repeated when the BIOS or one of the other bus enumerators informs the
configuration manager about a system configuration change.
Registry
Configuration
Manager
Enumerator
Device
driver
Arbitrator
Bus
Device
Device
Figure H.4
Configuration manager and example connection of devices
H.5 Virtual machine manager (VMM)
The perfect environment for a program is to run on a stand-alone, dedicated computer, which
does not have any interference from any other programs and can have access to any device
when it wants. This is the concept of the virtual machine. In Windows 95/98 the virtual ma-
chine manager (VMM) provides each application with the system resources when it needs
them. It creates and maintains the virtual machine environments in which applications and
system processes run (in Windows 3.
x
the VMM was called WIN386.EXE).
The VMM is responsible for three areas:
•
Process scheduling
-
responsible for scheduling processes. It allows for multiple applica-
tions to run concurrently and also for providing system resources to the applications and
other processes that run. This allows multiple applications and other processes to run
concurrently, using either co-operative multitasking or pre-emptive multitasking.
