User`s manual

General Information
1-23
1
Disk I/O Support
The debugger can initiate disk input and output by communicating
with intelligent disk controllers over the PCI bus. Disk support
facilities built into the debugger consist of command-level disk
operations, disk I/O system calls (only via one of the system call
instructions) for use by user programs, and defined data structures
for disk parameters (refer to Chapter 5 for information on system
calls).
Parameters such as the address where the module is mapped and
the type and number of devices attached to the controller module
are kept in tables by PPCBug. Default values for these parameters
are assigned at power-up and cold-start reset, but may be altered as
described in Default PPCBug Controller and Device Parameters on
page 1-27.
You can obtain a list of supported controllers with the IOI
command. Appendix E contains a list of the controllers presently
supported, as well as a list of the default configurations for each
controller.
Blocks and Sectors
The logical block defines the unit of information for disk devices. A
disk is viewed by PPCBug as a storage area divided into logical
blocks. By default, the logical block size is set to 256 bytes for every
block device in the system. The block size can be changed on a per
device basis with the IOT command.
The sector defines the unit of information for the media itself, as
viewed by the controller. The sector size varies for different
controllers, and the value for a specific device can be displayed and
changed with the IOT command.
When a disk transfer is requested, the start and size of the transfer
is specified in blocks. PPCBug translates this into an equivalent
sector specification, which is then passed on to the controller to