|Note 1||If the IBM EGA card is configured for an IBM 5151 monitor (MDA) or an IBM 5153 monitor (CGA), then ideally, pin 2 should be grounded (to meet the MDA/CGA standard).
Although a jumper (P1) is provided on the IBM EGA card to do just that, I have never found a requirement to use it.
|Note 2||Normally not connected, but in an early version of the IBM MDA that I have (dated 1982), pins 3/4/5 are connected to chip U64 and consequently are being driven low.
|Note 3||Mode 1 = 15.7 kHz, Mode 2 = 21.85 kHz
IBM's EGA monitor, the IBM 5154, automatically switches between Modes 1 and 2 according to the polarity of the incoming vertical sync pulses.
More information about Modes 1 and 2 follows.
|1.||Boot your computer into DOS.|
|2.||Because Mode 2 operation is in effect, you'll find that the 'V.SIZE 2' adjustment on the 5154 monitor rear works, but that the 'V.SIZE 1' adjustment does not.|
|3.||Run CheckIt software (either version 2.1 or 3).|
|4.||Select TESTS then VIDEO then GRAPHICS. A test pattern will show, using video mode 04.|
|5.||Because Mode 1 operation is now in effect, you'll find that the 'V.SIZE 1' adjustment on the 5154 monitor rear works, but that the 'V.SIZE 2' adjustment does not.|