Commodore Plus/4 Default Background Color On Power On

This article provides a definitive answer regarding the visual startup sequence of the Commodore Plus/4 home computer. It specifically identifies the default background color displayed when the system is initially powered on. Readers will gain insight into the technical specifications of the TED chip responsible for this output and understand how this color scheme distinguishes the Plus/4 from other contemporary Commodore machines.

When a Commodore Plus/4 is switched on, the screen initializes with a specific color palette determined by the Text Editing Device (TED) chip. Unlike the Commodore 64, which famously boots with a blue screen featuring light blue text, the Plus/4 presents a different visual profile. The default background color that appears immediately upon powering on the unit is light blue. This hue serves as the canvas for the startup message and the BASIC prompt that follows the memory check.

The TED chip, which integrates video and sound capabilities in the Plus/4, C16, and C116 models, manages the color registers during the boot process. Upon reset, the hardware defaults to a specific configuration where the background color register is set to a light cyan or light blue shade. The text displayed over this background is typically rendered in a darker blue, creating a monochromatic blue aesthetic that was characteristic of the TED series computers. This default setting remains active until the user loads a program that changes the color registers or manually adjusts the settings via BASIC commands.

Understanding this default state is important for retro computing enthusiasts and collectors verifying the health of their hardware. If a Commodore Plus/4 powers on with a different background color, such as black or white, it may indicate a modification to the motherboard, a specific cartridge is interfering with the boot sequence, or there is a fault with the video output circuitry. For a stock, unmodified unit, the light blue background is the expected standard behavior that confirms the video chip is functioning according to its original factory specifications.