Sarasota PC Monitor
by Vinny La Bash
Member of the Sarasota Personal Computer Users Group,
Inc.
We have all heard that the
more memory your system has the better. Does that apply to video RAM as well?
Not necessarily. Screen resolution and color depth are set from the Settings tab
in the Display Properties dialog box as shown in Figure 1. To calculate how much
video memory you need, you must know the color depth and the screen's horizontal
and vertical resolution in pixels. Here's the formula:
Minimum video memory = HR x VR x CD 8,388,608
where HR is the horizontal resolution, VR is the vertical resolution, and CD is the color depth. Let's dissect that equation for clarity.
Horizontal resolution (the number of pixels in a line across the screen) and vertical resolution (the number of horizontal lines on the screen) are the numbers used to describe screen resolution, such as 640 by 480, 800 by 600, or 1024 by 768. Multiplying them together yields the number of pixels displayed at a given resolution.
Color depth is the number of bits needed to support a certain number of colors. For instance, you need 8 bits to produce 256 colors (2^8 = 256). High Color can display 65,536 colors. This setting needs 16 bits (2^16 = 65,536). To calculate the number of bits for an entire screen, simply multiply the screen resolution (number of pixels) by the color depth. Let's calculate the minimum amount of video RAM necessary to support the option chosen in Figure 1. VRAM = (1,152*864*16) 8,388,608. That works out to 1.898 megabytes of video RAM.
Why divide by 8,388,608? Because video cards advertise their video memory in megabytes, and 1MB has 8,388,608 bits (8 bits in a byte times 1024 bytes in 1 kilobyte times 1024 kilobytes in 1MB). The resulting number is the minimum amount of video memory you need to support that combination of resolution and color depth. Of course, extra video memory doesn't hurt. It can be used to cache images for quick redisplay and improve video performance.
Screen resolution and color depth are increasingly a function of monitor size.
| Screen Size | Useable | Optimal | Minimum Video RAM For High Color Optimal Resolution | Not Recommended |
| 15 inch | 640 x 480 | 800 x 600 | 585KB | 1,024 x 768 |
| 17 inch | 800 x 600 | 1,024 x
768 1,152 x 864 |
1.5MB 1.9MB |
640 x 480 1,280 x 1,024 |
| 19 inch | 800 x 600 1,280 x 1,024 |
1,024 x
768 1,152 x 864 |
1.5MB 1.9MB |
640 x 480 1,600 x 1200 |
| 21 inch | 1,024 x
768 1,152 x 864 1,800 x 1,440 |
1,280 x
1,024 1,600 x 1,200 |
2.5MB 3.7MB |
640 x 480 800 x 600 |
These guidelines should prove helpful in providing the most pleasing viewing experience. We have not considered flat panel displays as they are still too expensive for general home use. Perhaps next year.
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Copyright 1998. This article is from the Novemer 1998 issue of the Sarasota PC Monitor, the official monthly publication of the Sarasota Personal Computer Users Group, Inc., P.O. Box 15889, Sarasota, FL 34277-1889. Permission to reprint is granted only to other non-profit computer user groups, provided proper credit is given to the author and our publication. We would appreciate receiving a copy of the publication the reprint appears in, please send to above address, Attn: Editor. For further information about our group, email: admin@spcug.org/ Web: http://www.spcug.org/
The Sarasota Personal Computer Users Group, Inc. has 1,000+ members and was established in 1982. We are members of the Assoc. of PC User Groups (APCUG), the Florida Assoc. of PC Users Groups, Inc., and we are members of the America Online Ambassador Program.
See http://www.spcug.org for all reviews from the Sarasota PC Monitor, go to the Newsletter Section.