Information Technology Reference
In-Depth Information
VMM32.VXD
Memory management JAVASUP.VXD
JavaScript
PPPMAC.VXD
PPP connection
NDIS.VXD
NDIS
NDIS2SUP.VXD
NDIS 2.0
NETBEUI.VXD
Net BEUI
NWREDIR.VXD
NetWare Redirect
VNETBIOS.VXD
Net BIOS
TCP
WSIPX.VXD
IPX
WSHTCP.VXD
In Windows 95/98, VxD files are loaded dynamically and are thus only loaded when they are
required, whereas in Windows 3.
x
they were loaded statically (and thus took up a lot of
memory). In Window 3.
x
these virtual device drivers have a 386 file extension.
Operating system
Universal driver
Mini-driver
Mini-driver
Hardware
Figure H.3
Device drivers
H.4 Configuration manager
A major drawback with Windows 3.
x
and DOS is that they did not automate PC configura-
tion. For this purpose, Windows 95/98 has a configuration manager. The left-hand side of
Figure H.4 shows how it integrates into the system and the right side of Figure H.4 shows an
example device connection of a PC. Its aims are:
•
Determine, with the aid of several subcomponents, each bus and each device on the sys-
tem, and their configuration settings. This is used to ensure that each device has unique
IRQs and I/O port addresses and that there are no conflicts with other devices. With plug-
and-play, devices can be configured so that they do not conflict with other devices.
•
Monitor the PC for any changes to the number of devices connected and also the device
types. If it detects any changes then it manages the reconfiguration of the devices.
The operation is as follows:
1. The configuration manager communicates with each of the bus enumerators and asks
them to identify all the devices on the buses and their respective resource requirements. A
bus enumerator is a driver that is responsible for creating a hardware tree, which is a hi-
erarchical representation of all the buses and devices on a computer. Figure H.5 shows an
example tree.
