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 NOTE: The information discussed in this article is based on features and functionality planned for a future release. The discussion of PPCP herein does not represent a commitment on the part of Apple Computer, Inc. for providing or shipping the features and functionality discussed. Information is subject to change without notice.
This information is taken from "Macintosh Technology in the Common Hardware Reference Platform", which is available from the PPCP Web Site:
http://chrp.apple.com/
Apple Computer and the PowerPC Platform
The PowerPC Reference Platform (PReP), Apple RISC architecture, and IBM RISC server systems were used in the development of the PowerPC Platform (PPCP) architecture. The objective was to reduce the porting effort of operating systems and applications coming from each of these environments. The information below describes the relationship of the Apple RISC architecture to the PPCP architecture and of the PowerPC Reference Platform to this architecture. The PowerPC Reference Platform used IBM RISC client and server information.
- Many components of the second-generation Power Macintosh architecture are included for compatibility with the desktop products based on that architecture. Features of the second generation Power Macintosh are listed below:
- Based on the PowerPC microprocessor family for main system processing. The instruction set of the Motorola 68LC040 is supported through a built-in emulation system.
- Use of the PCI bus to support all I/O and system expansion. Other buses (such as NuBus, SCSI and IDE) are supported by means of bridge ASICs connected to the PCI bus.
- Use of Open Firmware for system startup and to allow use of expansion cards from other architectures. While the Mac OS continues to be the principal operating system for Power Macintosh computers, Open Firmware lets other operating systems that are ported to the PowerPC instruction set take control of the computer.
- Function of processor bus coherency. Memory systems connected directly to the PowerPC bus, including main RAM and all levels of cache, belong to a single coherency domain.
- Support for both Big-Endian and Little-Endian addressing modes. Besides the support for both modes built into the PowerPC processor, storage subsystems such as frame buffers are accessible to software through both Big-Endian and Little-Endian apertures.
- Support for Macintosh-style I/O such as ADB, SCC and LocalTalk.
- Support for PowerPC-native interrupts and native device drivers.
Apple is currently designing computers that will comply with the PowerPC Platform specification. The following table lists the general characteristics of first- and second-generation Power Macintosh computers and the currently-projected characteristics of Power Macintosh computers that comply with the PowerPC Platform specification.
PPCP-Macintosh Feature Comparison
| Feature |
First-Generation Power Macintosh |
Second-Generation Power Macintosh |
PPCP Specification Power Macintosh |
| Processor Type |
PowerPC 601 |
PowerPC 601, 603 or 604 |
All PowerPC Models |
| Processor Upgrade |
None |
By replacing processor subsystem card |
By replacing processor subsystem card |
| OS Support |
Mac OS |
Mac OS |
Mac OS, OS/2, AIX, Netware, Solaris and Windows NT |
| External Cache |
Up to 1MB |
Up to 4MB |
Up to 4MB |
| RAM expansion |
32-bit SIMM |
64-bit DIMM |
64-bit DIMM |
| Maximum RAM |
72-264 MB |
1 GB-1.5 GB |
To be determined |
| NVRAM |
Macintosh PRAM |
8 KB |
8 KB |
| Support for 21-inch monitors |
None, 16 bpp, or 24 bpp |
16 bpp or 24 bpp |
16 bpp or 24 bpp |
| Sound |
Macintosh 16-bit, 44.1 MHz, stereo input and output |
Macintosh 16-bit, 44.1 MHz, stereo input and output |
Both Macintosh and SoundBlaster-compatible stereo input and output |
| Internal hard disk |
160 MB to 1 GB |
250 MB to 2 GB |
To be determined |
| Additional internal drives |
One 5.25-inch, one or two 3.5-inch |
One 5.25-inch, one or two 3.5-inch |
To be determined |
| SCSI buses |
1 internal, 1 external |
1 fast internal, 1 external |
To be determined |
| IDE bus |
No |
No |
Yes |
| Floppy disk format |
MFM or GCR |
MFM or GCR |
MFM only |
| Ethernet |
AAUI |
AAUI or 10BaseT |
10BaseT |
| Geoport serial ports |
2 |
2 |
1-2 |
| x86-compatible RS-232 serial ports |
None |
None |
0-2 |
| IEEE P1284 parallel ports |
None |
None |
In some models |
| NuBus slots |
1-3 |
None |
None |
| PCI slots |
None |
3-6 |
3-6 |
| ISA slot |
None |
None |
None |
Text version of PowerPC Macintosh Comparision Chart
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