IBM PC 100, Техническое руководство

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Chapter 4. System Compatibility
Hardware interrupt IRQ9 is defined as the replacement interrupt level for the cascade level IRQ2.
Program interrupt sharing is implemented on IRQ2, interrupt 0Ah. The following processing occurs to
maintain compatibility with the IRQ2 used by IBM Personal Computer products:
1. A device drives the interrupt request active on IRQ2 of the channel.
2. This interrupt request is mapped in hardware to IRQ9 input on the second interrupt controller.
3. When the interrupt occurs, the system microprocessor passes control to the IRQ9 (interrupt 71h)
interrupt handler.
4. This interrupt handler performs an EOI command to the second interrupt controller and passes control
to the IRQ2 (interrupt 0Ah) interrupt handler.
5. This IRQ2 interrupt handler, when handling the interrupt, causes the device to reset the interrupt
request before performing an EOI command to the master interrupt controller that finishes servicing
the IRQ2 request.
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 1.2 MB mode in either a 160/180 KB or
320/360 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 1.44 MB diskette drive.
Figure 31. 5.25-Inch Diskette Drive Reading, Writing, and Formatting Capabilities
Diskette Drive Type
160/180 KB
Mode
320/360 KB
Mode
1.2 MB
Mode
5.25-inch diskette drive:
Single sided (48 TPI) RWF — —
Double sided (48 TPI) RWF RWF —
High capacity (1.2 MB) RWF RWF RWF
R = Read W = Write F = Format
Figure 32. 3.5-Inch Diskette Drive Reading, Writing, and Formatting Capabilities
Diskette Drive Type 720 KB Mode 1.44 MB Mode
3.5-inch diskette drive:
1.44 MB drive RWF RWF
R = Read W = Write F = Format
Chapter 4. System Compatibility
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