128 Video Displays

I currently own a Commodore 64 computer and am thinking of upgrading to a 128. My only problem is that I have heard that the 128 can be used only as a 64 without the 1902 monitor. I don't see how this can be true. I know that without the 1902, the 128 can only display 40 columns and not 80, but is there any truth to not being able to use the 128 in different modes without the 1902 monitor?

Eric Mohn

The 128 has two video chips that produce two different video signals. The VIC II (8564) chip produces a composite signal, which is used in 64 mode and in the 128's 40-column mode. The other signal—RGBI—is generated by the VDC (8563) chip, which is responsible for the 128's 80column display. Either display mode can be used in 128 or CP/M mode.

You can display the 128's 40-column output on any composite monitor—color or monochrome. The 80-column output must have an RGBI display for 80-column color, but you don't necessarily have to have a Commodore 1902. The 128's RGB connector is the same as that on the IBM PC, so any RGBI color monitor that works with a PC will also work with a 128. The advantage of the 1902 is that it can display both composite and RGB video—a feature not found on many monitors. There's also another alternative. The 128 does provide a composite version of the 80-column video signal, but only in monochrome. You can get a good monochrome 80-column display using a composite monitor and a special cable available at most computer stores for this very purpose.