====== Hardware ======

The Bally Professional Arcade is a full-color videogame system based on the mass-RAM-buffer technique. A mass-RAM-buffer system is one in which one or more bits of RAM are used to define the color and intensity of a pixel on the screen. The picture on the screen is defined by the contents of RAM and can easily be changed by modifying RAM.

The system uses a Z80 microprocessor as its main control unit. The [[software:system ROM]] has software for four games: Gunfight, Checkmate, Scribbling, and Calculator. Additional ROM can be accessed through the cartridge connector. Three [[hardware:custom chips]] control the video interface, special video processing functions, keyboard and control handle interface, and audio generation.

The system exists in both high-resolution and low-resolution models. The three custom chips can operate in either mode. The mode of operation is determined by bit 0 of [[hardware:i o ports|output port]] 8H. It must be set to 0 for low-resolution and 1 for high-resolution. This bit is not set to 0 at power up and must be set by software before any RAM operations can be performed.

**NOTE:** The Bally Arcade only has access to low-resolution output. High-resolution output was available in certain Bally arcade titles. Further references to the high-resolution mode are omitted throughout the Better Bally Book. For further information about this mode, please consult the original Nutting Manual.


----

Hardware is divided into the following subsections:

  * [[hardware:Memory Map]]
  * [[hardware:Screen Map]]
  * [[hardware:Color]]
  * [[hardware:Interrupts]]
  * [[hardware:Magic System]]
  * [[hardware:Player Input]]
  * [[hardware:Music Processor]]
  * [[hardware:i o ports|Input/Output Ports]]
  * [[hardware:custom chips|Custom Chips]]
  * [[hardware:expansion|Expansion]]

----

Image source: [[http://www.ballyalley.com|Bally Alley]]