What is Planar Memory?

In computer graphics, there are several strategies that inventors use to increase resolution and accurate color while saving storage. While modern computers use high graphics cards capable of storing up to 32 GB of memory, an older and less appreciated approach to computer graphics is the planar method. This blog will discuss what planar graphics are, its pitfalls, and the current applications for this system.
 
Planar graphics operate by using several bitmaps of RAM to arrange pixel data. In this system, every bit is associated with one exact pixel. The distinguishing factor which sets planar graphics apart from other forms of organization, such as chunky, is that the data for an individual pixel is spread out across various bitmaps that make up the display.

Prior to higher-performing graphics cards, older memory chips could not supply enough data to display an image from a large bitmap onto a monitor. Planar graphics systems worked around this by storing the data in various planes, which could be stored by different memory chips.  With the data being split up between multiple chips, it could be read at a slower rate, allowing for an appropriate image to be displayed. While modern graphics systems and chunky displays store color values for each pixel contiguously, such as an RGB or BGR display, planar formats store each color component in a different plane. This was a critical difference in the 1980s and '90s because if the monitor only needed to display eight colors, a chunky display would assign eight bits to each pixel versus the three from a planar display.
 
The apparent advantage of a planar graphics system is the ability to save a significant amount of RAM. For example, on a 640x480 screen with 32 colors, a planar arrangement would only need 192,000 bytes versus the 307,200 bytes that would have otherwise been required. Additionally, planar graphics were also beneficial in allowing older programs to still run even after a system upgrade. For example, if a monitor was upgraded from a 16 to 32-color display, a planar arrangement would still allow 16-color games or programs to run. These programs worked because the software on planar-based systems could specify how many planes it wanted to use and completely disregard unneeded colors.
 
There are several technical disadvantages to planar graphics, which is one of the reasons they are rarely used today. The most significant drawback is that scrolling and other kinetic animations require more RAM address cycles to display correctly. On planar graphics systems, the display would flicker as text scrolled by or would temporarily change color. As the performance of graphics cards exponentially increased through the 2000s, and the number of colors used in displays increased eight-fold, planar graphics became nearly obsolete. Many of the planar graphics systems sold today are legacy pieces and are very rare. Examples of specific models include the Lenovo 02DC327, Planar SD2020, and Dell 1909Wb. The Commodore Amiga and NES, famous for their revolutionary color video games, were the first to popularize a planar graphics system.
 
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