Information Technology Reference
In-Depth Information
file systems and drivers. It is responsible for the queuing of file service requests and
for routing the requests to the appropriate file system driver.
•
Port driver
-
this component is a 32-bit, protected-mode driver that communicates
with a specific IDE disk device. It implements the functionality of the SCSI manager
and miniport driver.
•
SCSI layer
-
this component is a 32-bit, protected-mode, universal driver model ar-
chitecture for communicating with SCSI devices. It provides all the high-level SCSI
functionality, and then uses a miniport driver to handle device-specific I/O calls.
•
Miniport driver- in Windows 95/98 these miniport driver models are used to write
device-specific code. The Windows 95/98 miniport driver is a 32-bit protected-mode
code, and is binary-compatible with Windows NT miniport drivers.
Installable File System Manager
File System
Component
VFAT
CDFS
Block I/O Subsystem
I/O Supervisor
Other layers
SCSI Layer
Port driver
Miniport driver
Figure H.7
File system architecture
In Windows 95/98, the I/O Supervisor (IOS) is a VxD that controls and manages all pro-
tected-mode file system and block device drivers. It loads and initialises protected-mode de-
vice drivers and provides services needed for I/O operations. In Windows 3.
x
the I/O Super-
visor was *BLOCKDEV. Other responsibilities of the IOS include:
•
Registering drivers.
•
Routing and queuing I/O requests, and sending asynchronous notifications to drivers as
needed.
•
Providing services that drivers can use to allocate memory and complete I/O requests.
On Windows 95/98, the IOS stores port drivers, miniport and VxD drivers in the
SYSTEM\IOSUBSYS directory. The PDR file extension identifies the port drivers, MPD
identifies miniport drivers and VxD (or 386) identifies the VxD drivers. Other clients or vir-
tual device drivers should be stored in other directories and explicitly loaded using device=
entries in SYSTEM.INI. A sample listing of the IOSUBSYS directory is
Directory of C:\WINDOWS\SYSTEM\IOSUBSYS
AIC78XX.MPD AMSINT.MPD APIX.VXD ATAPCHNG.VXD
BIGMEM.DRV CDFS.VXD CDTSD.VXD CDVSD.VXD
DISKTSD.VXD DISKVSD.VXD DRVSPACX.VXD ESDI_506.PDR
HSFLOP.PDR NCRC710.MPD NCRC810.MPD NECATAPI.VXD
RMM.PDR SCSI1HLP.VXD SCSIPORT.PDR VOLTRACK.VXD
