Video Memory

Definition

In an electronic device (computer, mobile phone, etc), memory dedicated to the storage of the elements intended to be posted. It is usually named VRAM.

History

Historically, the originators of Ordinateur S quickly asked to lay out of a memory dedicated for the posting of the characters, and possibly graphs, separated from the general memory used for calculations and the storage of the programs. Indeed, they had specific integrated circuits intended to generate the signals of posting. These circuits were to respect a perfect Synchronization to them-even to agree with sweepings of the cathode tubes.

With this intention, these circuits must reach the memory at very precise moments, and do not suffer from interruptions of the main frame. This central Processor, can have tasks to him which, according to him do not make it possible either to have to wait (access storage Magnétique, network). In order to reach the memory of posting without entering in conflict with the main frame (which carried out calculations), a dedicated memory was allotted. This memory contained initially only the codes of the characters to be posted. The processor wrote, with the authorization of the circuit bill-poster, the new codes characters to the dedicated sites. With the next cooling of image, the processor of posting posted the new character.

Then, with the appearance of the graphs, this video memory was used to store characters, points, and possibly of the Vecteur S (description of a line by its starting point, arrival, and the widths and line colors). The writing of the points and vectors is done, according to architectures, by the processor, or the load circuit of posting.

Currently

In the advanced graphics cards of 2005, the video memory stores images (an image in the course of posting, another in the course of writing (which could be posted later), of the texture S (images representing of the “tapestries” of stones, wood, grass…), of the objects in 3 dimensions, etc the processor of posting assembles and animates these various elements.

Many cheap modern computers do not have specific memory for the video, but use a dedicated part of RAM. One speaks about shared memory.

Anecdote

In 1980, a video memory counted 1K with 2K Octet S. In a video memory of cellphone can reach several hundreds of kilobytes and the video memory of a graphics card of PC of 16 Mo with 16 Go of memory.

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