Specifications

Getting Started
UPGRADING FROM ZT 8806/8807 SYSTEMS
If you are upgrading your existing STD DOS system from
ZT 8806/8807 boards to the ZT 8809A DOS systems, you should be
aware of the enhancements introduced with the ZT 8809A DOS that
may affect compatibility with existing systems.
This section explains how the memory map and interrupt usage differ
between the ZT 8809A systems and the ZT 8806 and ZT 8816
Revision A STD DOS systems.
The ZT 8809A DOS memory map is designed for maximum
compatibility with the IBM PC hardware environment to ensure
portability of code. The full 64 Kbytes of DOS system memory is
now available. This made it necessary to move the ZT 8844 video and
ZT 8980 network BIOS extensions from address range 9C000h
through 93FFFh to address range C0000h through C3FFFh. The
PROM disk that resided in this area may now be configured for
address range 80000h through 9FFFFh, or disabled completely.
The STD-80 Series Bus Specification Revision 2.3 allows two
additional bus lines to be optionally used for backplane interrupts.
One signal, previously designated RESERVED*, is now referred to as
INTRQ1*. The other signal, CNTRL*, retains its original name. The
ZT 8809A DOS systems use the INTRQ1* line for keyboard
interrupts, leaving CNTRL* and INTRQ* backplane lines available
for the user. Therefore, frontplane cabling for multiple interrupt
support is not required.
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