Types of RAM Used for Video

Types of RAM Used for Video

 

You should be aware of the names of all types of RAM used on video cards.  Also note the following:

• Video cards using regular DRAM, VRAM, WRAM and MDRAM are no longer manufactured.
• SGRAM is still used on some very low-end cards
• SDRAM and DDR-SDRAM (often just called DDR RAM) are used in most available video cards and SDRAM is being phased out as the price of DDR-SDRAM drops.
• When you upgrade a video card, you need to upgrade the driver as well.

RAM	Characteristics
DRAM	Same type of RAM as used for system RAM Single-ported Inexpensive
Video RAM (VRAM)	First type of specialized RAM used for video Dual-ported More expensive than DRAM
Window RAM (WRAM)	Optimizes graphics functions Dual-ported Faster than VRAM Less expensive than VRAM
Synchronous Graphics RAM (SGRAM)	Synchronized to the system clock like SDRAM Single-ported Almost as fast as VRAM More expensive than DRAM but less expensive than VRAM
Multibank DRAM (MDRAM)	Uses 32 KB increments of memory rather than 1 MB increments (allows the possibility of less wasted video memory if slightly more than a 1 MB increment of memory is needed) Single-ported Uses an "interleaved memory" technique to provide speeds similar to dual-ported memory
3-D RAM	3-D logic processing embedded on chip Graphic card chip set passes data directly to 3-D RAM 3-D RAM can display graphics with or without involving the chip set
SDRAM	Same type of RAM as used for system RAM
DDR-SDRAM	Same type of RAM as used for system RAM

You should also know the following facts about color palettes:

• A color palette is the current list of colors that can be represented on the screen.
• Color shift occurs when incorrect colors are used to display an image because the color palette probably does not contain the proper colors.
• Color shift is common on display systems that use 4, 16, or 256 colors.
• To correct color shift, increase the color depth of the display system if the system will allow it.
• The amount of memory needed to display data depends on the screen resolution, the color depth, and alpha blending (color information enhancement).

Use the following table to determine video RAM requirements.

Video Resolution	4-bit Color Depth (16 colors)	8-bit Color Depth (256 colors)	16-bit Color Depth (65,000 colors)	24-bit Color Depth (16.7 million colors)	32-bit (24-bit True Color with 8/bit Alpha Channel)
640 x 480	256K	512K	1 MB	1 MB	2 MB
800 x 600	512K	512K	1 MB	2 MB	2 MB
1024 x 768	1 MB	1 MB	2 MB	4 MB	4 MB
1152 x 1024	1 MB	2 MB	2 MB	4 MB	4 MB
1280 x 1024	1 MB	2 MB	4 MB	4 MB	6 MB
1600 x 1200	2 MB	2 MB	4 MB	6 MB	8 MB