Chapter 6. System Compatibility
Diskette Drives and Controller
The following figures show the reading, writing, and formatting capabilities of each type of diskette drive.
Notes:
1. Do not use 5.25-inch diskettes that are designed for the 1.2MB mode in either a 250/500 KB or
300/500 KB diskette drive.
2. Low-density 5.25-inch diskettes that are written to or formatted by a high-capacity 1.2 MB diskette
drive can be reliably read only by another 1.2 MB diskette drive.
3. Do not use 3.5-inch diskettes that are designed for the 2.88 MB mode in a 1.44MB diskette drive.
Copy Protection
The following methods of copy protection might not work in systems using the 3.5-inch 1.44 MB diskette
drive.
Bypassing BIOS routines:
– Data transfer rate: BIOS selects the proper data transfer rate for the media being used.
– Diskette parameter table: Copy protection, which creates its own diskette parameter table, might
not work in these drives.
Diskette drive controls:
– Rotational speed: The time between two events in a diskette drive is a function of the controller.
– Access time: Diskette BIOS routines must set the track-to-track access time for the different types
of media that are used in the drives.
– ‘Diskette change’ signal: Copy protection might not be able to reset this signal.
Write-current control: Copy protection that uses write-current control does not work, because the
controller selects the proper write current for the media that is being used.
Hard Disk Drives and Controller
Reading from and writing to the hard disk is initiated in the same way as in IBM Personal Computer
products; however, new functions are supported.
Figure 34. 5.25-Inch Diskette Drive Reading, Writing, and Formatting Capabilities
Diskette Drive Type
250/500 KB Mode
300/500 KB Mode
1 MB Mode
Single sided (48 TPI)
RWF
—
—
Double sided (48 TPI)
RWF
RWF
—
High capacity (1.2 MB)
RWF
RWF
RWF
Figure 35. 3.5-Inch Diskette Drive Reading, Writing, and Formatting Capabilities
Diskette Drive Type
720 KB Mode
1.44 MB Mode
2.88 MB Mode
1.44 MB drive
RWF
RWF
—
2.88 MB drive
RWF
RWF
RWF
Chapter 6. System Compatibility
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