Specifications

CHAPTER 1
Introduction
2
The 12” and 7” PC Compatibility Cards are x86-based cards. You can plug the 7" card
into any Macintosh computer that has a PCI (Peripheral Component Interconnect) slot.
You can plug the 12" card into any Macintosh computer that supports a full-size PCI slot.
The cards provide the computer with full PC compatibility and the ability to run DOS,
Windows 3.1, and Windows 95. The cards perform identical functions; however, the
smaller 7" card can be plugged into CPUs with limited enclosure space. In addition, the
two cards have different microprocessors and PC/PCI chip sets.
Note
The 12" and 7" cards are referred to generically in this developer note as
cards, PCI cards, or compatibility cards. The functions performed by the
cards are referred to as PC system functions, as opposed to the
Macintosh system functions performed by the Macintosh host
computer.
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WARNING
12" and 7" cards are designed to plug into PCI slots in Macintosh
computers. Do not plug them into PCI slots in DOS- or Windows-based
PCs. In addition, you should use only one card (12" or 7") in your
Macintosh computer. It is possible to insert more than one of these cards
into a Macintosh with multiple PCI slots. However, if you do this, it will
compromise the functionality of the cards and cause problems with
resource allocation and I/O connections.
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The cards differ from previous Apple cards in this category in the following ways:
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They communicate with the Macintosh computer by means of the PCI bus rather than
the Apple RISC (reduced instruction set computing) bus.
■
They have enhanced microprocessors.
■
They have enhanced video capabilities.
■
They do not share user memory; that is, there is no portion of Macintosh memory set
aside for PC use. However, there is some memory sharing at a system level, where the
Macintosh computer and the PC can both access certain segments of Macintosh
memory. The Macintosh and PC use this facility to communicate with each other.
■
They have external L2 caches as well as the L1 caches integral to the microprocessors.
This chapter summarizes the features of each card and explains the functional and
physical characteristics. Figure 1-1 shows a simplified block diagram of the 12” card and
indicates how it interfaces with the Macintosh computer. The interface for the 7” card is
similar.