Video memory info

This memory is the one installed on the graphic card circuit board and its nature is somewhat different that the main computer memory. The graphic card memory is most of the time dual ported which means that two independent read or write operations can be accomplished simultaneously by the circuits accessing it. The graphic card components accessing the video memory are the graphic Chipset and the RAMDAC. Before the dual ported memory existed both of these component had to wait after each other before to access the memory so to overcome this problem the manufacturers developed the dual ported memory.

The dual ported memory is referred to by the name of VRAM or WRAM. The main differences between VRAM and WRAM is that the later has been specifically optimized to operate under a Windows environment so it is faster under this OS but the DOS performances of the WRAM under a DOS environment is close to the VRAM memory.

The important question about the graphic card video memory is "How much video memory is enough?".

Again, the answer to this question is very simple and can be found by the use of a small formula. The required amount of video memory needed is directly related to the screen resolution used multiplied by the color depth.

A more detailed explanation will be given here. Basically everyone knows that 1 byte = 8 bits. According to this we can now calculate that the 16-bits color mode (65k colors) will need 2 bytes to be stored into the graphic card video memory.

So, in regard of this the only thing we have to do is to first divide the color resolution number of bits by 8 to get the number of required bytes to be stored into the video memory and then multiply this value by the product of the horizontal resolution multiplied by the vertical resolution which gives the following formula;

M2D = color depth number of bits /8 X (vertical resolution X horizontal resolution) where M2D stand for memory size on a 2D graphic card.

For instance lets suppose you will use a screen resolution of 1280 X 1024 under the 16-bits color mode, then using the formula we will have:

M2D = 16/8 X (1280 X 1024) where M2D = 2.62mb so we will understand that the nearest memory size to use such a color depth and screen resolution will be 4mb because 2.62mb cant fit into a 2mb memory bank.

Note that this formula is only true in the case of a 2D graphic card.