Video monitors for the IBM PC
By. Patsch.
Patsch is a consultant specializing in the selection, evaluation and installation of IBM personal computer and compatible hardware and software.
Comparison Table
Figure 1. Specifications for the various monitors/adapters.
Several adapters and monitors can use different modes. These are typical
values for comparison. Two colors is monochrome: green and black.
The wide variety of video monitors for the personal computer can be con fusing. The first IBM PC used a mono chrome video monitor with a mono chrome display adapter (MDA) card.
Monochrome is the standard computer term for a B&W monitor. Monochrome monitors most often use green characters on a black screen. The IBM mono chrome monitor 5151 uses a high persistence green (P39) phosphor.
Amber on black monochrome monitors are a popular alternative to green on black. Some monitors use black characters on a white screen so they look like paper. These are used for word processing and desktop publishing (DTP) where the output is a printed page.
Adapter cards
Displaying information on a computer monitor requires a display adapter card, which is plugged into the PC; a cable to connect the card to the monitor; and a video monitor. The IBM MDA can display text but not graphics on a monochrome monitor. The Hercules graphics adapter (HGA) can display text and graphics on the monochrome monitor.
The HGA quickly replaced the IBM MDA when it was released. The HGA with a monochrome monitor is the most common display adapter and monitor for the PC, XT and AT personal computers. Some of the IBM compatibles have the display adapter built into the PC and do not require an adapter card.
The IBM PS/2 computers have the display adapter built in.
The IBM color graphics adapter (CGA) displays color text and graphics on the IBM color display 5153. IBM then introduced the enhanced graphics adapter (EGA) and the enhanced color display 5154. These color adapter cards use a 9-pin ROB digital output to drive the video monitor. The MDA and HGA also use a 9-pin digital output to drive the monitor.
The IBM PS/2 computers have the video graphics array (VGA) built in.
These use the IBM 8512 or 8513 color monitors or the 8503 monochrome monitor. The VGA output is a 15-pin analog signal. The PS/2 model 30 and 25 use a multicolor graphics array (MCGA) with the same monitors. The MCGA is a subset of VGA. Video monitors and display adapters together are often referred to as monochrome, CGA, EGA and VGA. For ex ample, the term EGA is often used to mean an enhanced graphics adapter with an enhanced graphics display.
Monitors
NEC introduced the MultiSync monitor, which can work with a variety of video adapter cards. The MultiSync monitor can work with analog or digital input, 15.5kHz to 35kHz horizontal scan, 56kHz to 62kHz vertical scan and 800 x560 (HxV) picture elements. It has a bandwidth of 30MHz. NEC and others have introduced several newer models with the multiple sync capability. Some of these models accept only analog input for use with the analog VGA output.
Several high-resolution monitors are used for desktop publishing. These monitors have a large screen area and use black characters on a white screen.
Typical specifications are 100MHz bandwidth, resolution of 1,280 x 1,024 or more, and 19- to 20-inch screen size.
These monitors are sold with a custom display adapter that can only be used with this monitor. Wyse, Cornerstone, Micro Display, Panasonic and others make these paper-white monitors.
IBM also offers an 8514 monitor with a matching 8514/A adapter card for the PS/2. The 8514 provides a 1,024x768 resolution on a 16-inch screen with 16 to 256 colors. The IBM 7554 color monitor is similar to the 8514, except that it has a 19-inch screen. The IBM 8507 is a 19-inch, monochrome, paper white monitor. These large, color screens are often used for computer aided design (CAD). Using video monitors with a personal computer is straightforward once you understand the different adapter cards and displays. Knowing the basic terminology and what the different video monitors are can help you set up the best system for your client's needs.