IBM 6275 - PC 300 GL, Техническое руководство

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Chapter 7. 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 either a 250/500 KB or 300/500 KB diskette drive for 5.25-inch diskettes that are designed
for the 1.2MB mode.
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.
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.
Figure 26. 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 Tracks Per Inch
(TPI)) RWF — —
Double sided (48 TPI) RWF RWF —
High capacity (1.2 MB) RWF RWF RWF
Figure 27. 3.5-Inch Diskette Drive Reading, Writing, and Formatting Capabilities
Diskette Drive Type 720 KB Mode 1.44 MB Mode
1.44 MB drive RWF RWF
2.88 MB drive RWF RWF
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Technical Information Manual