Video Electronics Standards Association
VESA, for Video Electronics Standards Association, is a group of representatives of the manufacturers of which the goal is to define video standards and to standardize certain components on the matter.
It is with this organization that one owes compatibility SVGA, resolution 800 X 600 Pixel S and higher, and the local drunk VLB. Thus, any software calling upon a view Vesa can function with any Graphics card SVGA compatible Vesa.
Frequencies of cooling
The committee also defined frequencies of cooling of screen, minimal for each resolution:
- In 640 X 480 Pixel S, the frequency must be equal or higher than 72 Hz.
- In 800 X 600 Pixel S, the frequency must be equal or higher than 72 Hz.
- In 1.024 X 768 Pixel S, the frequency must be equal or higher than 70 Hz.
information is to be confirmed
The local bus Vesa
The committee also defined the local bus VESA or VL-Bus to ensure a perfect compatibility between the expander cards VL-Bus and the computers laying out of a local drunk Vesa. It is about a standard bus 32 bits, with a speed of clock from 25 to 40 MHz.
Before this standardization, each manufacturer had developed his own local bus 32 bits what generated serious compatibility issues.
However this bus was limited by the number of Connecteur S available in the Central processing unit (three) and by a problem of configuration of the charts according to the speed of the Processeur - the frequency of bottom was the same one as the external frequency of the processor. However, it represented at the time a projection interesting for office automation and the CAM, compared to the bus ISA. It was remarkably replaced by the bus NCV, even replaced to him by port AGP for the graphic expander cards (the NCV makes it possible to connect other expander cards that charts vidéos). Currently, the tendency is again with the fusion of the ports of extensions, the NCV, the PCI-X (version of the NCV modified for the requirements in band-width for the waiters) and the AGP amalgamated in the NCV-Express train, very remote relative of the VLB…