Editing Macintosh II (section)

== Expansion & Connectivity ==

=== NuBus Architecture ===
[[File:Nubus-ppc950.jpg|thumb|NuBus Connector]]
The Macintosh II introduced [[NuBus]] as the expansion bus architecture for the Macintosh platform, providing six expansion slots for add-in cards. NuBus was originally developed at MIT and refined by Texas Instruments, offering a 32-bit multiplexed address/data bus operating at 10 MHz. This provided a theoretical maximum transfer rate of 40 MB/second, though practical throughput was typically lower.<ref>{{cite conference |title=NuBus: A Simple, Elegant, High-Performance Bus |conference=IEEE International Conference on Computer Design |year=1983 |pages=393-396}}</ref>

Key features of the NuBus implementation included:
* Automatic configuration with no DIP switches or jumpers
* Geographical addressing (each slot had a unique address range)
* Multi-master capability allowing cards to initiate transfers
* Fair arbitration ensuring equal access to the bus
* Support for block transfers and burst modes

=== Expansion Card Categories ===
The NuBus slots accommodated various types of expansion cards:

'''Video Cards''': The Macintosh II required a video card for display output, as it had no built-in video circuitry. Popular options included:
* Apple High-Resolution Video Card (640×480, 8-bit color)
* Apple Two-Page Monochrome Card (1152×870)
* SuperMac Spectrum series
* RasterOps ColorBoard series
* Radius DirectColor/GX cards