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System Support Functions
The Mark V motherboard has the following standard AT-compatible system elements:
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seven Direct Memory Access (DMA) channels,
• Channels 0 - 3 for 8-bit data transfer, and
• channels 5 - 7 for 16-bit data transfers.
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sixteen interrupt levels,
Supports eleven levels of interrupt:
IRQ3 - IRQ7, IRQ9 - IRQ12, IRQ14, and IRQ15.
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three programmable timers,
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a system clock,
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standard I/O capability, including:
• uses 32-, 16-, and 8-bit memory devices, and
• uses 16- and 8-bit I/O devices.
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I/O bus operating at 8 MHz for the 33 MHz Mark V and 10 MHz for the 40 MHz Mark V.
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8- and 16-bit IBM AT-compatible expansion slots,
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the standard I/O address space of 100h through 3FFh,
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24-bit memory addresses to access 16 MB of memory,
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uses the I/O channel check to generate an NMI,
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has I/O wait state generation,
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has an open bus structure (allowing multiple microprocessors to share the system's resources, including memory),
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allows system memory refresh from channel microprocessors,
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has a real time clock that is crystal controlled and has a battery back-up,
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provides a standard 5-pin IBM AT-compatible DIN connector for the keyboard,
● supports a hardware Deturbo switch,
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has a keyboard lock to prevent unauthorized access, and
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has a standard speaker attachment.
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